I was going to say that reptiles (including birds) have ZW females and ZZ males but there's actually a lot of variation that I didn't think about until I googled it. Apparently some reptiles use XY/XX, some do ZW/ZZ, and some rely on incubation temperature so there's a lot of options. To answer your question, as far as I can tell, all snakes are ZW/ZZ.
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