Complex sentence: In early 1942, Zyklon B had emerged as the preferred extermination tool of the Nazi regime for both the Auschwitz-Birkenau and Majdanek extermination camps during the Holocaust.
Split into simpler sentences: In early 1942, Zyklon B had emerged as. The preferred extermination tool of the Nazi regime for both the Auschwitz-Birkenau and Majdanek extermination camps during the Holocaust.