Being unable to comprehend Zorro's current or future powers doesn't make it insane.
After Zoro scarred Kaido he fought an opponent that harder to cut and damage than Kaido. Zoro obtained more power which you use to cut and defeat King. Any power that can damage King will cause Kaido even more damage.
Zoro defeating King's magma flame Dragon and King was preparing him to kill Kaido.
With King, everything was separate. The fire dragon, haki, durable body, and strong defense (wing) were individual layers Zoro had to get through to defeat King. With Kaido, everything's going to be combined into one.
The even a haters unintentionally support ZKK by sayings Zoro parallel Ryuma's dragon slaying feat by cutting down a fire dragon. They were just ahead of themselves and focus on the wrong fire dragon.
:cheers:
Insane is having a character die, their voice disappear. Then having to change their DF, magical powers, just to bring them back to life.