Zombies? In an MMORPG? That sounds like the sort of game I was born to play. Dead Frontier isn't such a bad name, either. There's no big developer or publisher behind it, just an independent group by the name of Jagged Blade Games.
The graphics remind me of 10tons' Crimsonland, which itself is worth a look if you cackle uncontrollably at the thought of killing swarms of monsters and collecting insane power-ups. It has co-op too.
Dead Frontier is currently in open beta and free, so there's no reason not to give it a go if you find the idea even a little bit interesting. The official website includes various Flash mini-games to provide an idea of how it works. It's not complex stuff, but it has made me think seriously about trying the beta.
Dead Frontier [Official site]