So I was getting in the mood for some Left 4 Dead lately and I was wondering if such a setting would work in Genesys. Does anyone know of a fleshed out Zombie setting (L4D, Romero style, Walking Dead, Resident Evil, whatever) or has played one and would care to share experiences?

I don't see why you couldn't. As with any generic system it will take a little tweaking to get the right 'feel' but it shouldn't be hard. I haven't played any zombie table top but their are a few out their that you can find reviews for. All flesh must be eaten, THE END OF THE WORLD: ZOMBIE APOCALYPSE, OUTBREAK: UNDEAD, are a few. I'd also look in to general horror rpg tips and such for gm's. The mood is about the same. Some times it is about the little things like checks for no reason, and big build ups to a room with horrible scratching sounds only to be a trapped raccoon, until they open the closet ahhhhhhhh! Have fun and if you get something together please share!

I don't know, but to me it looks very simple.

The creatures in general, in this kind of universe, is something easy to create. There are the normal zombies (minions), 4 or 5 special zombies (rivals) and 1 or 2 big big monsters (nemesis). The minions should (?) have a small move (a move or action per turn, impossible to use strain to move +1 cause minions don't have strain). But the hit is mortal.

Scarce resources : we have talked about this theses days. The game per se don't have a lot of ressources. In this case, have 2 things in mind: 1) It's possible to use a variant house hule that ammo or other things can finish with 3 or even 2 threats instead of a despair. It's up to the GM, and it's not like "EVERY double/triple threahts the character is out of rss". Use this few times. It's better to use to create other difficulties also. 2) Don't let the players use Story Points to find ressources as easy as in the normal game.

Ambient: use the things in modern campaing setting. No trouble here.