No, Suzuo is (was) also ZUO. Umashi is a separate person who wrote a fanfic that ZUO/Suzuo then drew an adaptation of. Basically, Umashi: writer; Suzuo/ZUO: artist.
This kind of drama and chemistry between Yuki and Raimu could honestly fuel it's own successful manga without the harem. As someone who struggles remembering my childhood I relate a lot to Yuki here, and Raimu is a really interesting love interest