Yeah, when he could not do damage, Zoro's go to was to unleash Enma more .
When Enma was unleashed and aimed at Kaido, Big Mom calls it a special blade that's dangerous and Kaido should avoid getting hit by it.
Enma's been the focus of Zoro's path to harming Kaido through out this fight.
That's not to discredit Zoro, just to point out that Enma is really important in the efforts to cut Kaido and cause significant damage.