The Tomb Raiser Zombies and Buckthead Mummies are pretty tough, plus, Flag Mummy Zombie can heal them, so the player needs to upgrade their plants.
Upgrade your plants' level by playing previous levels. Then upgrade them more with Puzzle Pieces and the Oven in your house.
Drag as many plants as you can into the lawn. Use other users' plants to have even more power. Remember to focus on your attack power. Charging plants like Potato Mine, Grave Buster or Iceberg Lettuce can be used to focus the attack on the Buckethead Zombie and one of the Tomb Raiser Zombies.