[2] After training as a banker from 1983 to 1985, Zielke attended the Georg August University in Göttingen from 1985 to 1990 and graduated with a degree in business administration.

[7][8] From 2006 to 2008, Zielke has been chief financial officer and member of the board of managing directors of Eurohypo,[9] which had been acquired by Commerzbank a few months before.

[12] Finally, in 2010, Zielke was appointed to the board of managing directors of Commerzbank, being responsible for the private customers segment.

[13][14] After having been appointed as Martin Blessing’s successor, Zielke took on the position of chief executive officer of Commerzbank on May 1, 2016.

[16] Although he had a contract until November 2023, he eventually resigned after disagreements with the bank's second-biggest shareholder, Cerberus Capital Management, in July 2020.