@badassgrunt88  
This pretty much whats stated in “the Zombie Survival Guide” and some other works.
 
Zombies can’t digest it, so it either causes there stomachs to eventually burst or it gets forced out the anus or mouth.

@Crowley  
Or their stomach just burst…

Real zombies - some form of uber-rabies, like in l4D…. Undead beings cannot exist, ergo, they are living, and need food to survive, and such transfer allows spreading of the virus. Let us look scientifically to it : yes, but maybe in small amounts of non-usable waste, and it’s not like they sit down and shit, it just comes out. That stink isn’t just the zeds themselves!

IF YOU ARE GOING BY ANY OTHER INFORMATION THAN THIS YOU ARE WRONG  

I can see zombies bring like that one anaconda in Ecuador. It tried eating a crocodile bigger then itself and it ruptured. Since zombies are already dead, a gaping hole in their gut wouldn’t slow em down. All the new food would just fall out the hole, but they’d keep on eating anyway.

No.  
They don’t even digest.  
Their desire of flesh is purely instinctual, but they don’t use the stuff they eat, nor they need it.

Does it matter?  
I thought not.

The zombies from the manga Franken Fran poop all the time, though that’s because they’re infected with a brain parasite instead of actually being undead. They’re also fully conscious of their predicament but have absolutely no control over their bodies.

@Crowley  
The L4D zombies aren’t actually undead. They’re just infected with what amounts to mutagenic super-rabies. They vomit all the time because that’s one of the symptoms of the disease.

a legitimate question!

I think it all just sort of, leaks out.

Scientifically, no. Their bodies are no longer alive, and therefore no longer functional. Ergo, no digestion actually takes place in their stomachs.
 
It could be said that the flesh the consume just marinates in their rotting guts, and when they’re hungry for more flesh, they throw up the “used” meat and hunt for more flesh to scoff. This also explains why some zombies (most notably from the L4D series) seem to vomit when being watched by survivors from afar.
 
Hey, you asked, Sweetie.

Good question. Depends on what kind of zombie though.

Uh…
 
Wow.
 
I don’t have a clue.

 
I HAVE NO IDEA!