Regarding the Rambam and shechita of tzedukim, the Chazon Ish discusses it in Yoreh Deah Siman 2. R’ Hershel Schachter says it over in a shiur at yutorah entitled “Q and A – Tanach, Textual Differences in the Torah, Deciding Halacha, Choosing a Profession” at around.
I was just going through that shiur again to quote in the Aruch Hashulchan thread, and I see here that I wrote “at around” without actually giving the time. So now I will rectify that: It’s at approximately 25:28.