Well we don't have any established criteria to judge whether one person's CoC coating is stronger than the other as of yet. So the debate of who has stronger CoC isn't really gonna get anywhere. That aside, I don't know if it's already been stated in this thread, but to me at least, it'd pretty obvious that the size of Zoro's CoC lightning is due to Haki overflow from Enma. I mean Zoro right now is not restricting Enma so it is using as much of his CoC as it wants.