2001–2005

Zimmerman began training aged 12 and competing in kickboxing in 2001 at the age of 15. He competed in the under-85 kg division early in his career before moving up, eventually reaching heavyweight.

On January 19, 2005, he won the Dutch Muay Thai title at 86 kg when he knocked out Bas van den Muijsenberg in Tilburg. He then followed this up with a fairly successful showing at the K-1 Canarias 2005 eight-man tournament in Tenerife, Spain on April 2, 2005. After knocking out local fighter Mario Ostos in the quarter-finals and Cameroon's Eric Kouman in the semis, he was defeated by Henriques Zowa via unanimous decision in the final.

He was able to bounce back by defeating Mutlu Karbulut in his next fight at It's Showtime 2005 Amsterdam on June 12, 2005. He was then given the chance to rematch Henriques Zowa at It's Showtime 75MAX Trophy, 1st Round - Tilburg on October 17, 2005. He was able to avenge his loss to Zowa, defeating him by unanimous decision after five rounds.

He ended the year with a second-round knockout of Omar Bellahmar on December 17 in Maastricht, Netherlands.

2006

Zimmerman began 2006 with a knockout loss to Naoufal Benazzouz on March 5. Despite this, he was still invited to take part in the K-1 Scandinavia Grand Prix 2006 in Stockholm, Sweden on May 22. In the quarter-finals, he defeated Jonathan Gromark via technical knockout in the extra round. Then, in the semis, he lost to Magomed Magomedov by unanimous decision and was eliminated from the tournament.

Following a round one TKO win over Michiel Gerlach on June 3, Zimmerman returned to the Canary Islands for the K-1 Canarias 2006 on June 16. He was unable to get as far as the previous year, however, as he was defeated by Gregory Tony on points at the first stage.

Towards the end of the year, he was able to pick up two more wins. He KO'd Johan Mparpagiannis in the first round at the K-1 World MAX North European Qualification 2007 in Stockholm on November 27, and took revenge on Naoufal Benazzouz by TKOing him in Roosendaal, Netherlands on December 9.

2007

Zimmerman kicked off 2007 by knocking out Jerry Hofman in Amersfoort, Netherlands on January 21. He then recorded the two biggest wins of his career when he took decision wins over K-1 veterans Brecht Wallis and Petar Majstorovic. He defeated Wallis in the Netherlands on April 7, and then entered the eight-man tournament at K-1 Fighting Network Romania 2007 on May 4 to make his K-1 debut. In the quarter-finals, he beat Majstorovic via an extra round majority decision before going on to rematch Wallis in the semis. He was unable to reproduce his earlier performance, however, and lost a majority decision.

On June 6, he KO'd Gurkan Demirmenci in round one in Tilburg, Netherlands. Zimmerman then defeated veteran fighter Rodney Faverus by decision in Arnhem, the Netherlands on October 14. He finished 2007 by TKOing Kenan Akbulut on November 17.

2008

On January 21, Zimmerman knocked out Orlando Breijdenburg in the first round at Ultimate Glory 7 in Amersfoort, Netherlands.

Then, on February 9, he took part in the opening round of the K-1 Europe Grand Prix at the K-1 World Grand Prix 2008 in Budapest where he faced Damir Tovarovic of Croatia. After the referee gave Tovarovic two eight counts in the second round, Zimmerman forced the referee to stop the fight when he rocked him for a third time with a high kick.^[4]

After stopping an aging Rene Rooze at the It's Showtime 75MAX Trophy 2008 on March 15, Zimmerman advanced to the final eight of the Europe GP at the K-1 World Grand Prix 2008 in Amsterdam on April 26. Against Attila Karacs in the quarter-finals, Zimmerman was given the TKO win when Karacs could not continue due to a cut on his shin. He then went up against Björn Bregy in the semis and, despite being dominated by the huge Swiss fighter in the first round and dropped in the third, was able to knock him out with a flurry of punches at the end of round three. Advancing to the final against Zabit Samedov, he took a majority decision win after a hard-fought three rounds to become the K-1 European Champion and qualify for 2008 K-1 World Grand Prix.^[2]

At the K-1 World Grand Prix 2008 in Seoul Final 16 on September 27, he beat Brazilian karateka Glaube Feitosa by unanimous decision (30–26, 30–26, and 30–26) to qualify for the K-1 World Grand Prix 2008 Final in Yokohama, Japan on December 6. In the quarter-finals, he faced Ewerton Teixeira, another Brazilian karate fighter, and took a majority decision (27–27, 29–27, and 28–27) to win over him. Then he went up against Badr Hari in the semis and was knocked out with a right straight in the third round.^[5]

On December 31, he took on Ikuhisa Minowa, a Japanese catch wrestler known for fighting much larger opponents, in a mixed martial arts bout at the annual New Year's Eve martial arts event Dynamite!! 2008 in Saitama, Japan. Minowa was able to take Zimmerman to the ground and submit him with a toe hold just over a minute into the fight.^[6]

2009

2009 was a relatively poor year for Zimmerman, as he fought five matches, losing three and winning two. He returned on March 28 against Peter Aerts at the K-1 World GP 2009 in Yokohama. He was able to take the Dutch legend into an extra round but lost via unanimous decision.^[7]

He then went up against Mourad Bouzidi at It's Showtime 2009 Amsterdam on May 16. Bouzidi was given the win when referee Joop Ubeda stopped the bout due to a cut on Zimmerman's knee in the first round.

Due to his standing as one of the world's best heavyweights, he was invited to the 2009 K-1 World Grand Prix. At the K-1 World Grand Prix 2009 Final 16 in Seoul, South Korea on September 26, he rematched Glaube Feitosa. After three rounds of fighting, Zimmerman was named the winner via majority decision (29–28, 29–28, and 30–30) and qualified for the final eight.^[8]

Between the final sixteen and final eight, Zimmerman took a fight against Wendell Roche at Ultimate Glory 11: A Decade of Fights in Amsterdam on October 17. He won by unanimous decision after an extra round.

The K-1 World Grand Prix 2009 Final took place on December 5 in Yokohama, Japan. He was unable to advance past the first stage as he lost to three-time K-1 World Grand Prix champion Remy Bonjasky by unanimous decision (30–27, 30–28, and 29–28) at the quarter-final stage.^[9]

2010

On April 3, Zimmerman faced Golden Glory teammate Semmy Schilt for the K-1 Super Heavyweight Championship at the K-1 World Grand Prix 2010 in Yokohama. Although Zimmerman was able to find Schilt's chin on a few occasions, Schilt dominated the match and took a unanimous decision (30–27, 30–27, and 30–28) win to retain the title.^[10]

He returned to the winning column on May 21, taking only twenty-four seconds to demolish Romanian fans' favourite Cătălin Moroşanu at the K-1 World Grand Prix 2010 in Bucharest.^[11]

He returned to the K-1 World Grand Prix for the third time on October 2 when he faced Daniel Ghiţă at the K-1 World Grand Prix 2010 in Seoul Final 16. He did not qualify for the final eight this time, however, as Ghiţă knocked him out less than twenty seconds into the second round.^[12]

In a superfight at the K-1 World Grand Prix 2010 Final in Tokyo, Japan on December 11, he dropped a unanimous decision (30–28, 29–28, and 30–28) to Ewerton Teixeira to bring his tally for the year to 1–3. Zimmerman looked out of shape during the fight, evident from his chubby body and breathing heavy after the first round. Because of this and his inconsistency he dropped rapidly from the top 15 world heavyweight kickboxers.^[13]

2011

Zimmerman returned to form in 2011, going undefeated at 6–0 over the course of the year. On March 19, he demolished Zinedine Hameur-Lain in just over thirty seconds in a superfight at the United Glory 13: 2010-2011 World Series Semifinals in Charleroi, Belgium. He totally overwhelmed the Frenchman with kicks and punches, breaking Hameur-Lain's left arm in the process, and forced the referee to stop the fight.^[14]

Then, in another superfight at the United Glory 14: 2010-2011 World Series Finals on May 28 in Moscow, Russia, he avenged his 2009 loss to Mourad Bouzidi by taking a unanimous decision over him.^[15]

Continuing his run of form, he knocked out Nikolaj Falin inside the first fifteen seconds of the first round of their contest in Merseburg, Germany on August 28.^[16]

Zimmerman was expected to face Hesdy Gerges at the K-1 World Grand Prix 2011 in Nanjing Final 16 on October 29. However, the event was cancelled with K-1 experiencing severe financial problems.^[17]

Instead, Zimmerman took part in a one-night, eight-man tournament in Oradea, Romania at the SuperKombat: Fight Club event on November 17. He won the tournament in devastating fashion, finishing all three of his opponents. In the quarter-finals, he knocked Sebastian van Thielen cold with a right hook before stopping German veteran Stefan Leko in the semis by referee stoppage. In the final, he knocked out the overmatched Roman Kleibl with a high kick just seconds into the second round.^[18]

2012

He continued his impressive win streak into 2012 with a crushing knockout over Rico Verhoeven at It's Showtime 2012 in Leeuwarden on January 28. He took less than a minute of round one to finish Verhoeven with a deadly four-punch combination.^[19]

He then faced Jerome Lebanner at United Glory 15 on March 23, and again demolished his opponent in the first round. Many fans are now calling for a rematch between Errol Zimmerman and Daniel Ghita, this time for the IT's Showtime Heavyweight Title. Since he lost to Ewerton Teixeira, Zimmerman is now 8–0, with 7 knockouts, 6 of which have come within the first round.

However his impressive winning streak came to a stop when he lost in a rematch to Semmy Schilt. Zimmerman did have his moments, where he rocked his opponent multiple times, but his lack of mobility and head movement made him an easy target for the much taller Schilt. He lost the match when his corner threw in the towel in the third round.

He competed in the sixteen-man 2012 Glory Heavyweight Grand Slam at Glory 4: Tokyo - 2012 Heavyweight Grand Slam in Saitama, Japan on December 31, 2012, but surprisingly lost to the unfancied Jamal Ben Saddik at the opening stage. He was floored by Ben Saddik in rounds one and two, but also scored a knockdown of his own late in the second. Time ran out just as he was making a comeback, however, and, due to the tournament's "best of three" format, he lost a unanimous decision after two, two-minute rounds.^[20][21]

2013

He rematched Rico Verhoeven at Glory 9: New York - 2013 95kg Slam in New York City on June 22, 2013.^[22][23] Despite Verhoeven being deducted a point for rabbit punching in round one, Zimmerman was not able to take advantage and lost by unanimous decision after being outworked and outstruck for three rounds.^[24]

He TKO'd Hesdy Gerges in round three of the tournament reserve match at Glory 11: Chicago - Heavyweight World Championship Tournament in Hoffman Estates, Illinois, United States on October 12, 2013.^[25][26]

He was knocked out by Daniel Ghiță for the second time at Glory 13: Tokyo - Welterweight World Championship Tournament in Tokyo, Japan on December 21, 2013, succumbing to a left hook at the 0:35 mark of round one.^[27][28]

2014

He was initially set to face Ben Edwards in the main event of Glory 15: Istanbul in Istanbul, Turkey on 12 April 2014^[29] but the match was transferred to the semi-finals of the Glory 16: Denver - Heavyweight Contendership Tournament in Broomfield, Colorado, US on May 3, 2014.^[30] He stopped Edwards in round one, scoring two knockdowns over the Australian, before giving an almost identical performance in the final against Anderson "Braddock" Silva as he knocked his Brazilian opponent down three times to win via another first-round TKO and take the tournament crown.^[31] Zimmerman stated in the post-fight press conference that he would have retired had he lost in the tournament.^[32]

2015

Zimmerman completed a trilogy of fights against Rico Verhoeven when he faced him on February 6, 2015, in the main event at Glory 19: Virginia.^[33] The anticipated bout ended in anticlimactic fashion as Zimmerman sustained a knee injury in the second round, allowing Verhoeven to retain his Heavyweight title.^[34]

Ten months later, Zimmerman fought Thomas Vanneste during Glory 26.^[35] Vanneste won the fight by split decision.^[36]

2016 and 2017

After this loss, Zimmerman left Glory and fought Viktor Bogutzki during Mix Fight Gala 20. He won the fight by a second round KO.^[37]

Errol then fought Murat Aygun for the WFL Heavyweight title, but lost the fight by decision.^[38] A month later, Zimmerman entered the A1 WCC Heawyweight Qualification Tournament. He beat Rinus Douma by decision in the semifinals, but lost to Adnan Redžović by KO in the finals.^[39]

Zimmerman then fought a rematch with Zabit Samedov, which he lost by unanimous decision.^[40] Zimmerman stopped the losing skid with a first round knockout of Luca Panto.^[41]

2018

Zimmerman fought twice in 2018. He lost a decision to Patrick Schmid in the A1WCC Champions League Heavyweight Tournament, and lost by KO to Nidal Bchiri during Enfusion 70.^[42]

2020

Zimmerman is scheduled to fight Rade Opačić at ONE: Big Bang 2, following a two year layoff.^[43] Zimmerman lost the fight by knockout in round 2, failing to beat the ten count after being knocked down by a spinning heel kick.^[44]