Ok here's the deal. We have a Zombie outbreak that spreads Rapidly, and these zombies are strong and fast, and able to spread their Zombie-ness through bites. At the same time a large number of Velociraptors (nee Deinonychus) Escape from Jurassic park to the mainland, and start laying eggs. ALSO at the same time, a huge number of T-100 Terminators armed with laser blasters teleport back from the future with laser blasters to start the Robot Holocaust early. And finally, at the same time the First class of Space Marines is commissioned, complete with all of their hardcore weaponry (think Aliens) and they are deployed across Earth and Space to deal with all of these threats to humanity.
The Zombies are spreading, and the Raptors are breeding. Also, the Terminators picked up the Borg trick of creating Cyborgs, and can "assimilate" living humans. The Zombies can Zombify the Raptors and the humans. No one is sure if the Cyborgs can be zombified, or if Zombies can be assimilated. Apparently, Zombie Raptors can still heal. Space marines have all of the firepower in the universe at their disposal, and can pretty much destroy anything fairly quickly. Also, more classes of Space marines are graduating every month. So I ask you; who wins? Oh, and all sides start with even numbers.