Because brain tampering to force compliance isn't really,, the BEST way to work a romance-

Basically uh-

Zims can be lacking in observation but-- well LOOK at Zib. He wasn't going to be able to pose as a regular ol Zim forever, and he especially can't keep up the charade 24/7 for Number 2. NO Zim is THAT stupid. So Zim1 and Dib1 cooperated with eachother for probably the first time since becoming Zib, in the interest of self preservation. Zim1 handed over intimate knowledge of PAK technology, and Dib used it to fuck around with Number2's brains a bit.

So- Zim2 has very little compulsion to kill Zib- or- well- Dib1. Any compulsions to do so he DOES have, he is literally incapable of acting upon due to Zim1's interference (usually via overwhelming his PAK with garbage directives until he can't function or literally just zapping him; and since Zim2 doesn't actually know WHAT or WHO exactly Zib is- he doesn't realize it's Zim1 / Zib doing it at all)

So yeah- Zim2 can kill anything that isn't Zib (although he'd probably get his ass kicked for killing another Zim because THEY NEED THEM FOR THE PLAN)

So yeah- I'm not sure if turning off the "I want to kill you" side of his brain to make room for literally any other thoughts turning both of them into a codependent dumpster fire of confusion, spite, and desperate need for purpose and validation is really,,, something you can tag under romance. Not gonna stop me tho I need more like-minded people in here and I have to find them somehow. They kiss and shit anyway it's fine

Oh also a light clarification/reminder:

Zib is the joint but separate consciousness of Dib1 and Zim1, I usually refer to them as Zib for simplicity because I'm referring to them both as the entity that is Zib.

Dib1 is in a relationship of sorts with Zim2

Zim1 is not in any kind of relationship with Zim2 outside of using him as a punching bag