Zoro will always be stronger than Sanji, but the cook Is not as behind as they want to be and what's worse Is putting characters like Mihawk, Rayleigh ecc above the likes of Prime Garp. This manga Is not about Zoro, Is about Luffy and that's also why characters like Lucci, Kidd and Law MIGHT be above Zoro, which Is something Zoro fans should not get mad about, Oda makes characters linked to Luffy as stronger, Zoro Is important but he's still inferior to his captain and his rivals generally.
Zoro, according to Oda himself is the Piccolo of One Piece, Just because Piccolo and Goku were equal for some time this doesn't mean that Piccolo Is above the likes of Vegeta (Kidd and Law), right?
And yes, Vegeta Is a good way to describe Kidd and Law, especially the bu saga one, who was below SSJ3 Goku (like Kidd and Law are to Nika Luffy).