Except that the Nazis did not use chemical weapons, and there is some controversy among historians as to why. It is commonly thought that the Nazis feared that the allies would retaliate in kind, and so didn’t use chemicals. Others claim that Hitler had an aversion to gas warfare because of his WWI experience…either his own injury from gas, or because gas is unreliable in the battlefield. Goering once told his interrogators that the Nazis had no way to protect their draft animals from gas, and so didn’t want to get chemical warfare started as they were so heavily reliant on horse drawn transport.
Whatever: Hitler did not use chemical weapons.
Zyklon B is not a chemical weapon. It is an industrial pesticide used by the Nazis to murder people. Murdering people who have been rounded up and imprisoned is not warfare.
It is disgusting that, in your eagerness to score political points, you blur the line between warfare and the wanton mass murder of captive people.