I mean of COURSE zoro knew luffy would never ever just *leave* a nakama and let sanji go get married just like that with just a BRB note that was obviously a lie. There's no way *I* would believe that zoro would actually believe that in earnest. And even if zoro actually hated sanji, especially enough to want him off the crew, it would have made more sense for him to go with luffy and keep him from bringing sanji back. Warn sanji off, make sure he knew he wasn't wanted.
If he harbored actual real genuine hatred towards sanji, he would have gone to WCI just to kick his ass for making luffy and Nami and Chopper and brook put themselves in danger for his dumb ass. He would have gone to WCI if he thought they COULDN'T get sanji back without him there, since sanji marrying pudding would let big mom have an arguable claim to power over the strawhats.
And if he thought it would put his crewmates in danger in any way for him not to go to WCI with them, he wouldn't have gone ahead to wano with law. Not unless he thought it would be *more* dangerous for them with him there.
I think zoro didn't want to go cause he knew it was supposed to be a stealth mission. And that making a scene would put everyone in danger. And that whatever shit show of a family sanji must have to have basically *lied to his crew* to make himself seem like an orphan before he was adopted by zeff, despite having an entire alive family - whatever would make him so scared he would abandon his nakamas, not trust them to save him, even after the whole Robin thing at enies lobby, after they *declared war on the world government* for one of their own -
I think zoro didn't think he could keep himself from just going batshit insane trying to kill all of sanji's family the first time he heard any shitty detail about how they treated him as a kid. And that wouldn't have been very stealthy at all