I said before, Oda is a Japanese, so he will make the shogun of Wano as one of the strongest characters in the series. We already saw how strong the real shogun of Wano aka Oden is. In fact, Oden's strength surpassed my expectation.
Now, among the strawhats, Oda gave all the strawhats real world nationalities. In Zoro's case, Oda said, he would be Japanese. Do you know the meaning of this? Do you understand how much national pride is involved with Zoro and Wano for Oda?
To be honest, I was a little skeptic about Zoro fighting Kaido myself. But the way things are going, all we have left is getting a narration box like =>
People say, in Oda's One Piece, never bet against Zoro