Three sounds, three trails. You don't see impact "stars" because you can't actually see Zoro clearly; his head for one is completely obscured.
Whatever Oda wants, I won't say that each is a substantial enough injury that we'll see exactly three wounds on Zoro and he's never been very consistent in that regard anyway. But I'm very confident that we'll see blood on his head and shoulder. Tbh... I'm not sure why anyone wants to split hairs over this. Like Sanji's balls will shrivel up and fall off if somehow Zoro has more than one entry point.