Oda showed that zoro is inferior to Oden by the inferior scar he gave to kaido.
Once again he should how zoro is inferior to oden when he couldn't control enma.(this were even admitted by zoro himself).
But when zoro got ACOC and controlled enma, he finally surpassed oden.
This will be shown when he beheads kaido.
I think zoro will take another mink medicine from chopper, this time it only lasts a minute or so and just enough for zkk to happen.
Then zoro goes to coma or some shit.