Here is the full list of all 13 I, Zombie achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
Collect 40 stars
Collect 20 stars
Turn 10 soldier into zombies
Lose a zombie
Die for the very first time
Turn a human into zombie
Finish the game
Collect 60 stars
Beat all summer levels with total time lower than 15 minutes
Beat all winter levels with total time lower than 8 minutes
Collect 90 stars
Finish all winter levels
Play at least one community level