Plants vs. Zombies Garden Warfare

This achievement is fairly simple to unlock.
As the description implies, "get every zombie class to level 5" meaning the:
1) Foot Zombie
2) All Star
3) Engineer
4) Scientist
In total it adds up to 20 levels.
- The quickest way to get this achievement is to buy sticker packs and hope that you get "skip stars"
- "Skip stars" allow you to skip any single challenge for one character (I suggest saving them for more difficult challenges).
- The more expensive the sticker pack, the better chance you have at receiving "skip stars".
ALSO, if you do get "skip stars" using a higher priced sticker pack, you receive twice the amount of "skip stars" cards than you would from the 1,000 or 5,000 sticker packs.