Zoro blocks a combined attack from two Yonkou in their strongest forms (bar potential awakenings) for long enough to let all the other 4 Supernova escape:
I don't think Kaido can give them an extreme diff fight, not unless he has Awakening.
The Roof Five faced him and Mama in their strongest known forms for 30minutes+,
while their two heaviest hitters were substantially holding themselves back:
- Zoro was fighting with a single sword
- Zoro still has Santoryu
- Zoro still has Asura
- Luffy was fighting in Base
- Luffy still has G4
- Luffy has "King" attacks for his G4 forms
I don't see how Kaido by himself gives the Roof Five an extreme difficulty fight. Hell, even though it was but for a moment, Santoryu Zoro managed to hold back the combined attack of the two Yonkou (and he withstood the attack no worse for the wear afterwards).
Together, Kaido and Mama showed the Supernova hell, but the Supernova powered through that hell. Alone? I would be thrilled if Kaido can give them a high difficulty fight.