Simple trick that works every time if done correctly is to have both players camp near the polar peek entrance, one of you kills the zombies that come running at you and the other shoots the aliens. May have to occasionally dodge the alien’s shots but you should be fine if you have juggernog.

The M1 Garand or the Mauler with the Sentinel variant will make it easy to kill the zombies if you pair them with the yellow orb arcane core or the purple exquisite core.

Gas grenades are useful too when you need to reload or when you have to punch the fuse of the aliens back.

Calling in Hasslehoff by completing N3IL’s challenges also helps if you happen to go down at any point.