Seriously! Its not really hard. its more as easy when you got the right strategy and knowledge.

Bobsled Bonanza:

Very nice game indeed ^v^.

My stratergy to win this fast and repeatedly is to put 4 Twin sunflowers at the back on the pool and 8-10 Cattails with Tall-nuts in front of them. Also , you should put Pumpkins at the four cattails which is the closest to the right because Zombies will emerge from the water at the final wave. No need for Spikerocks or Spikeweeds or even Jalapenos! Because this build is Quite expensive, I Start of killing zombies with Tangle Kelps, Potato Mines, Imitater Potato Mines and Squash at the first Wave.Then you start building you 8-10 Cattails.Note that it is not so hard. But Pogo Party is Harder.

Zombotany :

Same Strategy as my bobsled Bonanza! Exept that you Don't have to worry about the Vaulting Zombies. I also start off killing zombies with instant kills too.