Sanji couldn't even beat Page One. Who's Who is more than enough of a fight for him.
As for Kanjuro, he was only pretending to be weak. As we've seen, he is actually far stronger than what he's shown and I honestly think he could be YC3 level.
Zoro's grudge in wano was built up, not against Kaido, but rather with Orochi. This was done through his relationship with Yasu and Hiyori. Him fighting someone from Orochi's crew has much more build up than him fighting a beast pirate. Kanjuro, being a member of the kurozumi family, is likely Orochi's right hand. He has a major part to play in Kaido's rise to power and Oden's death and has been sabotaging the alliance from the beginning.
In his fight, Kanjuro will use his powers to bring back ryunosuke but with good artwork, basically summoning a kaido-style dragon. By defeating Kanjuro, Zoro will follow in Ryuuma's footsteps of slaying a dragon.