Zyklon B was actually a commercial pesticide used to fumigate buildings since the 1920's, when the Nazis repurposed it for murder. The manufacturers were prosecuted after the war. But most of the big german companies that were part of the murder machine got off easy. Bayer, of Bayer Aspirin, BAE, BASF, Audi. See https://en.wikipedia.org/wiki/List_of_companies_involved_in_the_Holocaust