[8] On 27 April 2003 Zimling made his Brøndby debut, coming on as a 76th-minute substitute, in a 3–1 win against Aalborg BK in a Danish Superliga game.[19] He made his first appearance of the season, coming on as a 68th-minute substitute, in a 0–0 draw against FK Ventspils in the first leg of the UEFA Cup second round qualification.[26] He made his debut for Esbjerg fB, starting a match and played 76 minutes before being substituted, in a 2–0 loss against FC Nordsjælland on 28 August 2005.[34] The 2006–07 season proved to be a breakthrough for Zimling, as he continued to establish himself in the starting eleven, playing in the midfield position for Esbjerg fB.[58] Ahead of the 2008–09 season, it was reported that Esbjerg was going to offer Zimling a new contract, but the club's chairman Jørgen Jensen denies this and expected him to leave in January.[64] When his contract set to expire in December 2008, it was announced on 20 July 2008 that Zimling would be moving to Serie A team Udinese on a free transfer and will join the club in January.[66] At one point, Esbjerg fB and Udinese both reached an agreement to fast-track Zimling's transfer in August, but the compensation prevented it from happening.[72] At one point, he went back to Denmark to finalize a possible transfer,[73] but the deal never materialized and he stayed at Udinese, who ultimately wanted to keep him.[75] However, once again, Zimling's first-team opportunities were limited once again, due to emergence of midfield talent like Gökhan Inler, Gaetano D'Agostino, Christian Obodo and Fernando Tissone, as well as, his own injury concern.[77] On 27 January 2010 he made another first team appearance for the club, coming on as a late substitute, in a 1–0 win against A.C. Milan in the quarter–finals of the Italian Cup.[88] Two weeks later on 5 March 2011, Zimling received a straight red card for a serious foul on Aleksandar Radosavljević, which the club lose heavily 5–1 against ADO Den Haag, resulting in him serving four games.After two-years at Belgium, Zimling joined Bundesliga side Mainz 05 on a four-year contract, which will keep him until 2017 and the deal believed to be worth around £1.75million.[112] Zimling made his debut for the club on 2 February 2013 against German giant Bayern Munich, coming on as a 62nd-minute substitute, in a 3–0 loss.[126] On 1 September 2014, it was announced that Zimling was sent on loan to Dutch Eredivisie side Ajax until the end of the season, with an option to buy.[127] He made his debut for the club, coming on as a 61st-minute substitute for the injured Nicolai Boilesen, in a 2–1 win against Heracles Almelo on 13 September 2014.[128] Four days later on 17 September 2014, Zimling made his UEFA Champions League debut, coming as a second-half substitute, in a 1–1 draw against Paris Saint-Germain.[132] On 1 February 2016 it was confirmed that Zimling was loaned out to FSV Frankfurt for the rest of the season due to lack of playing time.[135] However, in his third appearance for the club against St. Pauli on 19 February 2016, he ruptured his anterior cruciate ligament and was substituted in the 19th minute, as FSV Frankfurt won 3–1.[148] After serving a one match suspension, Zimling returned to the starting line–up and captained the club for the first time against Jammerbugt in the Round of 16 of Sydbank Pokalen, in a 4–1 win.[157] After missing two matches due to suspension, Zimling returned to the starting line–up against Vejle on 5 October 2018 and scored his first goal of the season, in a 3–0 win.[169] On 27 August 2021, Zimling made his comeback as a player, when he was in the starting lineup of Kolding IF in the Danish 2nd Division match against Middelfart Boldklub.[175] Zimling appeared in the next two matches to help Denmark U17 reach the knockout stage, but the national U17 side were eliminated from the tournament after he missed the penalty in a shootout in a 4–3 defeat against Spain U17 on 4 May 2002.[196] He played the rest of the qualification alongside his childhood friend William Kvist on the Danish midfield, as Denmark qualified for the UEFA Euro 2012.[199] But Zimling was given an injection and made his first appearance of the UEFA Euro 2012, against Netherlands on 9 June 2012, starting the whole game in the tournament, as the national team won 1–0."[202] Zimling then featured two more matches in the tournament for the national team, playing in the left–back position against Portugal and Germany, as they were eliminated in the Group Stage.[203] He made one more appearance by the end of the year, coming against Slovakia on 15 August 2012, starting a match and played 45 minutes before being substituted at half time, as Denmark lost 3–1.[205] The following day, he made his first appearance for Denmark in five months, starting a match and playing 80 minutes before being substituted, in a 3–0 loss against Macedonia.[206] A month later on 22 March 2013, Zimling scored his first national team goal, in a 2–0 win against Czech Republic for the 2014 FIFA World Cup qualification.[208] Following the national team's failure of qualifying for the World Cup, Zimling made two more appearances, coming against Norway and England.[211] Zimling is in a relationship with his long-term girlfriend, Christina, and became a first time father in April 2012 when she gave birth to a baby boy, Oskar.
Zimling playing for Bundesliga side
Mainz 05
in 2013.