I think some misunderstand, Zoro
can deal with flying characters fine, in fact he proves it, he says he needs to do something to reach King in the sky, what does he do next? He summons a tornado so big it eclipse 3 of Kaido's.
The problem is King durability, he is so durable it is said to be above Dinos and then step further, Dragons, he is at the pinnacle of defense so to speak, atleast his wings. We know Zoro though, there is nothing he can't cut!
He is going to overcome overpower King's durability. This will be set up for what he will need to do at the end of the arc.