I think it is time to lift Zoro from top 5 to top 3. 
The sole reason why he isnt above everyone is because he lacks effectiveness in cutting extra hard things.
Kaido's body and Mihawk's Yoru are probably the only two things he cannot cut enough to win.
He literally bested Kaido, the nr1 of the verse, in combat in 1vs1 and cleanly cut him.
The only reason why Kaido isnt history is toughness of his body, not because he is better than Zoro.
Nobody else is as tough as Kaido or Mihawk's Yoru. Zoro is far bigger of a beast than I imagined.