go reread chapter 1036, he is fighting king in some panels without CoC coating but just with flames or no flames in between, I think someone already posted those panels.
Also, why does it matter as the whole fight post chapter 1033 is Zoro fighting with KoH. Or are you saying his KoH was ON and OFF in the fight?
So, if flames is not KoH, then KoH is not a mode, it is just attack with different variants.
Besides, what 'invisible' haki Lucci used that has not used by Zoro?