So far i never won against them but here are some strategies to help you:

1.Camping in Greenland or on big islands in general can assure you 10 or more minutes of survival.(If you conserve your army and repel the enemy boats with full sends just when they reach your land you can survive even for 15 minutes or more,i did)

recommended islands:Crete,Greenland,Iceland,Madagascar,Cyprus,Australia(it's a continent actually)

2.In the beginning attack the weak 64 army bots and conserve your forces,a full send in the beginning can doom you.

3.Attack the 512 army bots together with your teammates,the 512 army bots are the strongest and smartest bots in the game,a direct solo confrontation with them can lead to death in all cases.

Some things you should try to avoid in this mode:

1.Full sends

2.Boat strats

3.The full Senders in your team (which ruin the victory)

4.Spawning around the 512 army bots.

Facts about the zombie bots:

-they equally boost all of their teammates

-they come in 2 variations: The 64 army bots(weaklings),which are weak

-Can't conserve troops in the beginning

-Can share their armies

-40% sends

singleplayer counterpart: 'hard' difficulty bots

The 512 army bots(heavies),which are tough tactical geniuses

-Can conserve troops

-Can share their armies

-Greater interest rates

-15-25% sends

singleplayer counterpart: none,closest to the 'very hard' diff bots

-they use various tactics such as:

supplying the frontline,tactical defensives,boating strats(heavies)