No, Zyklon B is/was an irreversible cholinesterase inhibitor, similar to other insecticides and binary nerve gases. It's mechanism of action is to inhibit the breakdown of acetylcholine at nerve endings, essentially making the parasympathetic nervous system fire without stopping (for the purists, there are exceptions--this is basic). The mechanism of action of cyanide is to replace oxygen on the heme (oxygen carrying iron) portion of hemoglogin, starving cells of oxygen.
You are incorrect. You are thinking of Sarin, a nerve gas produced by the Nazis, not Zyklon B. Concentration camp victims were not killed with nerve gas, but with Zyklon B. Zyklon B was an insecticide carrying hydrogen cyanide.
Zyk·lon-B [z? klon b?] nounhydrogen cyanide gas: hydrogen cyanide released as a gas from pellets, used originally as an insecticide and later as a deadly gas by the Nazis during World War II
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