Completion Strategy:

Like the 2 previous Behead The Undead Challenges, you have to kill a number of zombies until you die.
In Day Of The Dammed, you are situated in the room of Siberia, where you obtained the computer disk.
There are no weapons avaliable in this level, so you have to punch out the zombies.
One hit to the head results in decapitation, meaning a kill.
There is no radar, so make sure you look around to see if there are any zombies behind you.
Also, make sure you don't exit the room, because then you'll have 3 seconds to come back.

- Lenny

Platinum/Fast Time Strategy:

Platinum is very easy... even without gaining a single perfect, it's still easy.
If you would like a very high score, (60k+) what I suggest doing is to earn perfects on Wave 1-5.
It's fairly easy. During the first wave, the zombies will only be coming from the hallway ahead.
Perfect is easy to get.
On the 2nd wave, zombies will start to come from he hallway, and 2 will spawn from the 2 front corners once in a while.
On Waves 3 and above, zombies will come from the hallway, and from all 4 corners of the room.
I currently have a score of 166,200.
What I did was smash all the windows after Wave 1.
This prevents the zombies from walking into them.
Why is that good? Its good because if they walk right into the glass, they get dizzy, and it's hard to kill them, as they walk kind of crooked.
Also, there's this glitch where sometimes the zombies will spawn from behind the room first, instead of the hallway.
If so, take care of then.
It is unknown what exact Wave this glitch occurs in, as I have seen if occur in different waves.
Sometimes, if there are so many zombies in the area zone at once, I walk through the entrances, and come back through another one. Be careful though, as I did this once at 106k, and I didn't make it back in the 3 seconds... :(

Overall, platinum is a sinch!

- Lenny