Some zombie skins are not tagged as such in the kumos wardrobe, so when I'm searching specifically for zombie skins, they simply don't show up. The ones I've noticed are all four of this year's skins, as well as all four of last year's skins.

Side note, I had to post this here because I can only access the Wardrobe subforum from Kumos, and for some reason It keeps erroring out with "bad gateway" when I try to post it there.