I'm not sure, but it looks different from Advanced Haoshoku we have seen. Usually it flows out of the tip of the blade, but Zoro seems to be emitting it from nowhere in specific.
It's 100% CoC coating. That's why those fodders were knocked out. Using Haki in dangerous amounts is needed to tame Enma, so when Zoro gave everything he had he subconsciously flowed his Conquerors Haki on top of that to achieve maximum effect.