I don't think Luffy would deteat Zolo with the same ease by which he defeated Kuro, I think Zolo would give him more problems honestly. Whilst you could say Zolo got more of an improvement than Luffy when they fought on Whiskey Peak due to his fatal wounds, I think Arlong's reaction to Zolo implies this latter was at least a threat to him, so I think Luffy would have a bit more problems when dealing with his swordsman. Kuro's speed could be a problem, but I think Zolo would sort that out somehow or another, maybe exploiting his senses and the spinning attack his sowords beget.