Yeah, zombies would be rough but we have to assume they are slow and stupid like raw animals. The survival plan there is fairly obvious though it really would come down to how long they can survive with no brains if they can in fact starve to death given they are the undead.
Aliens would be rough because they have greater technology, likely they'd pretend to be our friends first to steal our raw resources so it wouldn't be an immediate war.
I always think of survival in terms on what happens if we get a Jericho scenario or even if we go hunting for the weekend and someone gets disoriented.