-100 or 500 map. Half Players vs Half AI (Zombies)
>>> there are no zombies in AI provinces until peace day is over, giving the chance for players to expand.
-For zombies 2 options..
Option 1: Either the spawn rate starts at x1 then goes faster every 10 days, on the 20th day, (when clock strikes half time) there's be peace for 5 days, then will start again with x3 after 10 days goes x4 (spawn rate for players is x2) until time runs out.
-Option 2: zombies spawn 2 troops instead of one per province. every 5 days, they increase to 3.. then 4, then 5.... (when clock strikes half time) you have peace for another 5 days. then begin with 6 and so on until max cap 10. until time runs out. (spawn rate is x4 speed for players.) until time runs out..
====(when clock strikes half time)= zombies stop spawning for 5 days
optional: When zombies are in battle with players... If the player were to lose their group of troops. 1/4 of those troops become zombies. Example. 20 troops vs 25 zombies. zombie wins, They gain 5 zombies from the 20 troops that died.
-Zombies well automatically start spawning and start attacking players after peace is over, but can only attack (no building)
2 options for Players:
Option 1: If they want to have an all fought out war, then all building cost nothing or cost 80%/90% less resources to build... But still has their same timing to build. (unless you want a challenge no vehicles)
Option 2: normal game play and everyone has to trade to stay alive.
-having peace in between the waves to recover= zombies will stop spawning and you have 5 days to quickly rebuild your defense or regain lost land or expand again. Because more will be coming.
-Zombies movement has no slowness side effects. Overseas: zombies has no slowness side effect... (think your safe on your island? Think again!)
Rules:
WIN: Players have to survive until time runs out to win or Clean out the zombies.
-gameplay timeline 2 or 3 months.
Lose: All players provinces are gone
(I think 5 days of peace is a good start) To give players enough time to build your defense or expand quickly in order to recruit more troops, before the horde comes. Once peace time is up! Zombies will start attacking everyone.
players you decide: make a wall? expand for more recruits? Work together? or be the only survival?
Not sure which would be better, to have everyone scattered across the map or close to one another at start of game.
(Personally) I think It'll be fun to have players scatter, when your over run. Its your ideal to retreat to a safer location to other players and work together. fight together or die alone. Then again being close to one another working together makes it fun as well.
(Special request to have a model for the zombies!) 
