Dagnabit, all the good answers are already taken!
and Unquestionably in agreeance!
Although I’ll suggest waiting for the rings to level up Zimkitty,
or if you pick up that 8th set of hidden blades, go ahead and level up Wilbur first
I have two Wilburs (one a +15, the other unleveled yet) A grazul (3/70) but no Zimkithas. (mutter-mutter-grumble with teeth gnashing) I hate facing the ones that I’d most wish to have.
Zim is a great hero, Grazul could be great for a 4-1 stack. But i would also consider the Elena’s costume, so wait one week longer to see you’re so lucky to get it