The decision came a day after a 1-0 defeat to Hertha Berlin left the Bundesliga's only ever-present club inside the bottom three of the German top flight.
'The best option'
"Joe Zinnbauer performed his duties here with great passion and maximum effort from the very first day," said Hamburg's sporting director Dietmar Beiersdorfer. "He gave everything for HSV. We've thanked him for this. After the recent results and in view of the overall sporting situation, though, we felt we had to make a change."
Zinnbauer has been replaced by Knäbel, who has been appointed until the end of the current campaign. "We're convinced that this is the best option in the current situation," said Beiersdorfer, who will present the new coach at a press conference on Monday. "Peter knows the team and the surroundings better than anybody and he is capable of acting immediately."
Zinnbauer passed on a message of support to his successor. "I would like to wish the team, Peter Knäbel and the club all the best for the season's run-in," he said.