So most of us ASSUME kaido has some type of zoan. Especially with his commanders and army. He's a bit obsessed with zaons, and REALLY wanted a dragon duplicate zoan. Plus he has ties to wano.
So if he did have a zoan, most of us would assume it's the original dragon. In Japanese mythology dragons are "the strongest creatures" and have some immortality.
If this is the reason kaido can't be killed, than couldn't blackbeard using dark fruit, negate his zoan or df, making him vulnerable and than BAM QUAKE TO THE MF DOME
thoughts
So if he did have a zoan, most of us would assume it's the original dragon. In Japanese mythology dragons are "the strongest creatures" and have some immortality.
If this is the reason kaido can't be killed, than couldn't blackbeard using dark fruit, negate his zoan or df, making him vulnerable and than BAM QUAKE TO THE MF DOME
thoughts