So you're claiming what? They were using Zyklon A? That's a new one.

https://link.springer.com/chapter/10.1007/978-3-319-97999-1_8

On the measure of eliminating postmortem indicators of a violent death, gassing was clearly preferable to using firearms because it did not leave the horrific wounds produced by the early mass shootings. But different types of gas produced different results. Kurt Gerstein (the Chief Disinfection Officer) argued that carbon monoxide gassing left a greater mess than Zyklon-B. When the doors of the carbon monoxide chamber opened, “the bodies were thrown out blue, wet with sweat and urine, the legs covered with excrement and menstrual blood.” 49 For this reason, Höss preferred Zyklon-B:

There was no noticeable change in the bodies and no sign of convulsions or discolorations. Only after the bodies had been left lying for some time, that is to say after several hours, did the usual death stains appear in the places where they had lain. Soiling through opening of the bowels was also rare. There were no signs of wounding of any kind. The faces showed no distortion.

This doesn't really sound like a hydrogen cyanide death at all.