In a 25-minute closing statement to the court on Thursday, Zuendel called for an independent commission to be set up to investigate how many Jews were killed by the Nazis.
He said that if the findings of the commission proved him wrong, "I will apologise publicly in a press conference to Jews, Israelis and the entire world."
Zuendel lived in Canada for several decades and fell foul of authorities there for his anti-Semitic opinions. He was extradited to Germany in 2005.
The trial was suspended in late 2005 after the judge dismissed a publicly appointed defence lawyer when she produced written submissions that appeared to deny the Holocaust. It resumed just over a year ago.