I think turning swords black is more of a COA thing which is why guys like Roger and Rayleigh do not have black blades even when they're just as powerful as Mihawk if not stronger. I totally can't see Zoro turning Enma black against King. ZKK may help him accomplish it, if it happens that is.
Zoro even having a shot at the n1 alr defies the typical arc format so it wouldn't be a big surprise if he defies it even more
My thinking is that Oda doesn't set up a curbstomping like what was in this chapter, if he isn't going to highlight Zoro getting stronger in some way.