I believe they did at least according to the British;
From the Wikipedia article on Zyklon-B:
After the war, two directors of Testa Bruno Tesch and Karl Weinbacher were tried by a British military court and were executed for their part in supplying the chemical.
Zyklon-B is still manufactured to this day, actually, believe it or not.
Also from the Zyklon-B Wikipedia entry:
Zyklon B is still in production in the Czech Republic in the factory Draslovka Kolín a.s. in the city of Kolín, under the tradename Uragan D2, and is sold for the purpose of eradicating insects and small animals. The Czech word uragan means “hurricane” or “cyclone” in English
I forgot to provide you with the link; this is from the company website (in English)
I tell people that Zyklon-B is still manufactured, under a different name admittedly, and lot’s of folks think I’m telling ‘em tall tales.