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.
Play at least one community level
Collect 90 stars
Beat all winter levels with total time lower than 8 minutes
Finish all winter levels
Collect 60 stars
Finish the game
Beat all summer levels with total time lower than 15 minutes
Collect 40 stars
Collect 20 stars
Lose a zombie
Turn 10 soldier into zombies
Die for the very first time
Turn a human into zombie