I think the big failing with Zamasu is I don't think the series did a good enough job explaining why Zamasu thought a world with no life was "perfect". I get that he thinks mortals often trend towards wrong-doing in his eyes but I felt they never really sold why he felt "nothingness" was better than anything else. You can't have perfection if you have ........ nothing. I would have at least liked some character to call him out on that.
What you forget to account for is that Zamasu would still exist, and he is perfect bishie husbando.