Ah yes king of “it takes 3 admirals to take down kaido” lightning. Even I, as a kaido super fan believing he is the strongest atm think it’s a bit extreme. No top tier is getting out of fighting 2 other top tiers. Let alone 3.
This is a WEEKLY manga, of course scale wouldnt make sense some times, specialy when we are dealing with things the size of mountains.
What we know for sure is that even Don Chinjao who is a pretty old pirate and used to fight prime Garp was impressed with Zoro's ability when he cut Pica in half, and lets not pretend he only cut Pica once, he slashed that bitch up until he had nowhere left to run, lets not forget Zoro dosent has a DF to help and at the same time hinder him, soo everything he does is pure haki and phisical ability, Law would need to be inside his room, wich is already pretty damn taxing on his stamina, just to be able to compete with Zoro. And since its proven that Law cant just cut anything inside his room like he couldnt cut Dofffy, it wouldnt even be much an issue for Zoro to beat Law, lets not forget that Law's slashes wouldnt hurt Zoro since the slashes from his df dont realy do any harm per say, but one slash from Zoro and Law=dead.