Okay, so you're looking to do a sort of Horde style Army. Here's what I can recommend:
1) Do not use small units of zombies. If you're going to field them en masse make sure you have them in large units. Small units will fold or be obliterated from the first charge, so they're pretty useless.
2) Heavy Cavalry. Zombies in a massive block can take some pretty devestating charges (to a point) and hold the unit in place. You're going to need a heavy cavalry unit or two to break up your opponents outlying units and come back through to charge his strongest attack piece from the flank or rear.
3) Beef up your Necromancy. You'll want spells that let you raise undead. You have paper soldiers which are really easy to kill, and you'll need to be able to summon more of them. You're going to harass his units so they're not going to be very mobile.
4) If you're fighting an army with massive amounts of ranged firepower you're going to need fast shock troops, something VC is NOT notorious for.