These are even harder challenges and some contain luck.
Here they are:
Have a Jack-In-The-Box Zombie eat your brains
Get 1000 flags in vasebreaker endless
Clear pogo party without tall nuts or magnet shrooms(Sproing!Sproing achiment)
Fill The lawn with Winter Melons
Fill all Zen Gardens with one of each plant avalible
Hynotise Your Zombatar