Hermione would win. She's the best in her year, and Malfoy is in the same year as Malfoy. But against Snape I dunno. If Hermione beat Malfoy, and Snape stepped in, he would defeat Hermione, and between Moody and Snape, I would say that they would do loads of damage to each other, but I wouldn't be sure who would win.
Yes, Hermione could easily take down Malfoy in a duel, and if that fails she could just punch him again. Really he's just a bully, and if he doesn't have the element of surprise or his goons, he is in trouble. But if it went beyond that.... hmmm. Snape would probably be able to stop her before she managed to cast a single spell (like with Harry) so it would be Moody or Snape. Both terribly skilled, but Snape seems alot deadlier, and Moody is only human, he is a wee bit unbalanced, was locked in a box by a death eater, was knocked out in the big battle in the Department of Mysteries... and besides, Snape's probably kitted out with potions like the luck one. In the end Snape takes it.
Well, perhaps, although Dumbledore pretty effectivly established he didn't have that killer instict. And in a straight up duel he still would have to contend with the fact Hermione is alot better then he is, what with all that DA training and other stuff, and his death spell abilities would be questionable if he loses his wand in the first moment before he gets the chance to do anything. Or if he is paralised or whatever.
i think that hermione could take down malfoy easily cuz she's really quick thinking and would act before malfoy could, but i really don't think she could kill just make it so he can't fight. then snape would step in and hermione will fight for a while weakening him but then she would either get killed(cuz i really don't doubt that he would kill her) or injured to badly to fight. then moody would go in for hermione and defeat the already weak snape. but i'm not sure if moody would kill snape. i think he only would if he really had to.