Zoro started pre timeskip with fishman, then monet, then pica, then kamazo, then ...kaidou? does it make sense?
as comparison,luffy started with hody, then CC, chinjao, then doflamingo, then cracker, then katakuri, then kaidou.
hody>>fishman
cc>>monet
doflamingo>>>>>>pica
katakuri>>>>>kamazo
if zoro beats kaidou, he already surpassed mihawk without facing him, since kaidou was called the strongest pirate