The son of a social democratic Upper School Board attended the grammar school 'recommendation studied from 1945 at the University of Hamburg and received his doctorate in 1951 with Hans Peter Ipsen. While studying the SPD member Zeidler in 1946 was co-founder and first secretary of the Federal Socialist German Student Union (SDS ).
After the exam Zeidler initially worked as a judge at the district court and the administrative court of Hamburg as well as in the administration of the Free and Hanseatic City of Hamburg. In the meantime, he was seconded as a research assistant at the Federal Constitutional Court, before he himself judge of the highest German court in 1967.
1970 joined Zeidler for five years as President to the Federal Administrative Court in Berlin. Then he returned to Karlsruhe and in 1983 became the president of the Federal Constitutional Court. This office he held until his adoption into retirement in November 1987.
From 1979 he was chairman of the German - British Lawyers Association. In 1986 he was also appointed Honorary President of the German -Korean legal society.
New Year's Eve 1987 Zeidler died in a climbing accident in South Tyrol.
- Impact of the West German state constitutions on the Bonn Basic Law. Dissertation. Hamburg 1950
- With Theodor Maunz, Gerd Roell corner (ed.): Festschrift Hans Joachim Faller. Beck, Munich 1984, ISBN 3-406-09597-6