You think Zoro would have got ACoC without Enma on Onigashima?
Yeah;
It’s just that Oda’s route for making Zoro’s CoC coating acquisition believable is through Enma. For Luffy, it was making the realisation that you could use CoC that way after getting hit by Ragnaroku.
If Oda never came up with Enma, he would have found another way for Zoro to get CoC coating.
Because in the end, Zoro’s next step in growing was to get that ability.