I
He was going after him with Yoru he mentioned he doesn't use a Canon to hunt rabbits when he used his small knife to lol diff Zolo
and he knows Shanks respects Luffy and knows Luffy is Zoro's captain, there's no reason for him to use a knife on him
yet he didn't use Haki or an any named attacks
remember, by that point, Mihawk already met Luffy