Just as a historical note, they didn’t use Zyklon-B in these early “proof-of-concept” death camps. They instead used exhaust fumes from tank engines.
Years ago I worked in an area close to a library. My job was manning the phone mostly. I took up reading autobiographies of survivors of the death camps. After 4 or 5 I had to stop.
The Nazis and even so capos were some real sick evil bastards. The stuff Mengele did was beyond barbaric. Injecting kids with all kinds of stuff etc.,
Zyklon-B was first used at Auschwitz on Russian POWs, in tests.
They were so successful, that it was decided to expand the camp and to build the larget crematoria to use it.