Yeah I think Zoro needed to find a way to maximize the usage of Enma instead of draining his haki and being used against King, which translates badly to a dragged out fight, hence why King would very likely beat him. While CoC helped him in that regard while dishing out a lot of damage in a short time to take advantage of King's off flame mode.
Perhaps the wound he inflicted (on his chest) could be used even when his flames get turned on as King was seen later blocking his sword with a basic kick but his chest bleeding. Kinda like what Franky did on Sasaki but on a different extreme.