I'm going to quote an SMG customer support person on how zombies work "How many troops they draft depends on which condition they are in terms of troop total. One is if they have the most, two is if they don't have the most. You can also see that not attacking them also results in some more ambitious troop gain as well. The troop placement tends to be fairly evenly spread. When they have below a certain percentage of territories they also have an increased probability of a "takeover" of another players territory."
Well Zombie placement doesn't affect your rank at all.
Losing to them if all other humans are gone is still a first place finish.