My interpretation is asura is not CoC because of Zoro's statement, "he put everything he had into that attack."
These scenes reminds me of Luffy scenes when he first awakened CoC haki.
Zoro
Luffy
They put everything they had into their attack or yell in Luffy's case, which included CoC haki, and not realize it.
Of course, that could change when we obtain more information about Zoro's CoC and asura.