He can make a SUPERFICIAL WOUND that kaido DIDNT EVEN REMEMBER after 5 SECONDS and thats using his strongest attack with usage of ACoC hence why kaido calls zoro a conqueror, he saw man using ACoC with all his might to cause a ridicolously weak wound on his body and since kaido has a heart too, he couldnt help, but congratulate the man for his effort, although meaningless:
Like a pitbull that feels proud for a chihuahua brave enough to attack him, even tho he knows the little mutt can't stand a chance against him.
THAT SHOULD BE ENOUGH FOR YOU!!!!!!!