Prime Rayleigh~Kaido~Mihawk>Current Rayleigh
Rayleigh fucked with Kizaru and Mihawk is likely stronger than that, seeing as they're both swordsmen. Mihawk also super casually sent an attack Jozu's way at Marineford, which Jozu somewhat struggled to deflect. He's far above Jozu's level, to the point where he should shrug him off in a fight like a Yonkou would. Mihawk also travels alone throughout the Grand Line, which I think gives an idea of how strong he probably is. I also can't see Zoro finishing the series not being able to take out a current Yonkou (with high diff), seeing as the current Yonkou are all weaker than prime WB/Roger and the Strawhats are probably going to bring things back to that level and Zoro is often close to Luffy's power and will probably be one of the strongest swordsmen in history, so needs to be able to hang with any potential Yonkou swordsmen in the heavens.
I'd guess that Mihawk would take it.