The moment of Zoro rounding up the samurai is coming closer. People thought Oda threw that out there for nothing...
King is simply a better fighter than Kaido. Kaido relies too much on his hardness and that wont save him long against Zoro.
King is actually able to keep up, for now at least. He will need a lot more to push Zoro to extreme diff, that happened only once.
And it was because Zoro's entire skill set was completely useless against Mr1.
King seems to be very tanky tho but unlikely to tank Zoro's high-end moves.