What is Reddit's opinion of
Zombie Defense?
From 3.5 billion Reddit comments
Popularity Score: 8
This app was mentioned in 8 comments, with an average of 1.50 upvotes
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Haven't played these myself, just did a quick Google search and compared game play clips
https://play.google.com/store/apps/details?id=com.HomeNetGames.ZombieDefense
https://play.google.com/store/apps/details?id=com.JESoftware.LastHopeTD
https://play.google.com/store/apps/details?id=com.HomeNetGames.ZombieDefense
Can't remember if it had the to-be-the-zombie mode, but the rest of the description fits.
Edit: didn't read the last part apparently so now I'm thinking; Probably this isn't it, because also no online function as far as I know.
Zombie defense, I love this game,but it's not a path tower defense game
https://play.google.com/store/apps/details?id=com.HomeNetGames.ZombieDefense
Evil Defender
https://play.google.com/store/apps/details?id=ru.crazypanda.EvilDefendersFree
And there is another one that I don't remember
I know you already found the one you were looking for, but I wanted to put this out there, Zombie Defense is one that sounds like you describe.
I didn't see an ambulance, but Zombie Defense on the play store might be what you are looking for.