This one still counts if you surrender. So you can create a very strong map, invite a friend, and then
and choose surrender as soon as you enter the map. You don't even need to start the first wave.
Achievement can be buggy if you are not the host. I got it in a friend's game, but it was troublesome. For best results, you should be the one to invite a friend. Remember you can copy a map in the lobby by pressing X --after you've been invited, but before the game starts.
Let me know if this gets patched or changes, please.