Stage 3-4

Zombies

 * Zombie
 * Conehead Zombie
 * Buckethead Zombie
 * Pole Vaulting Zombie
 * Newspaper Zombie
 * Ducky Tube Zombie
 * Snorkel Zombie

First Play
Select plants:
 * Sunflower
 * Potato Mine
 * Puff-shroom
 * Lily Pad
 * Wall-nut
 * Peashooter
 * Snow Pea
 * Repeater or Threepeater

Start planting Sunflowers. Plant Puff-shrooms at the front to slow down zombies. Once you can afford to without interrupting Sunflower planting, use Potato Mines on the first few zombies. Once you have more sun, add Peashooters on the third spaces from the left, then Snow Peas on the fourth spaces. When Snorkel Zombies arrive, plant a Wall-nut on the sixth space from the left in front of it, or use Puff-shrooms if the Wall-nut is not ready. Add Repeaters or Threepeaters on the fifth spaces from the left later.

Outcome

 * Crazy Dave's Car keys/Bacon
 * Big Trouble Little Zombie (Stage 3-5)