I am designing a campaign for a group of friends were there are several group of vampires. Because of the nature of the place they are there is also a lot undead (zombies, skeletons, ghost). i then began to wonder if vampires can also snack on zombies? Do zombies even really have blood? is this like freeze dried meat or more like someone trying to drink spoiled milk? what do you think collective let me know? 

Vampires drink blood as a source of life energy. The blood in Zombies is coagulated rotting goo... Nothing to gain from this.

In my opinion, Vampires need 'living blood'. 

Even a relatively new zombie will have coagulated rotting goop for blood. Some will spurt the black and brown junk when injured.

Vampires in my game don't bleed. They can get cut, the cuts just close themselves up.

I ran a vampire the masquarade campaign a few years ago, Vampires that only drank from animals were referred to as "Vegetarians", the Ventrue clan of vampires had very specific tasts and could only drink certain types of blood (either a particular blood type; a, b etc or a blood from a fearful target etc) and drinking blood from a dead creature might cause some form of physical degeneracy (change in skin/hair quality, teeth becoming dull/blunt etc).

So drawing on that for inspiration you could have some homebrew some manifestations for drinking blood, so Vampires drinking mostly from animals may take on some animalistic characteristis (grow whiskers instead of a moustache/beard, eyes look like a cats etc), drinking forma acorpse or zombie makes them look decrepid/rotting (see Clan Nosferatu and Samedi from Vampire the Masquarade).

It could also then give you some political intridues between vampire groups.

I would rule that:

1. Zombie Hearts do not not pump, so no gushing blood
2. Do have blood in their body parts
3. Thickens as the zombie 'ages'
4. No longer counts as 'human' blood, so things like vampires and mosquitoes can not feed on them.

Quote from Ankhrizing >>

I am designing a campaign for a group of friends were there are several group of vampires. Because of the nature of the place they are there is also a lot undead (zombies, skeletons, ghost). i then began to wonder if vampires can also snack on zombies? Do zombies even really have blood? is this like freeze dried meat or more like someone trying to drink spoiled milk? what do you think collective let me know? 

 I can see some Vampire sitting in an ornate chair with a zombie standing next to him. The vampire peels pieces off and chews it like zombie jerky. LOL.

Wasn't in Anne Rice's Interview with a Vampire drinking blood from a dead person could actually kill a vampire? I didn't read the books, but saw the movie a long time ago.

I would think that, no, zombies don't have blood, or at least not drinkable blood, no matter how fresh the corpse was.