Board Thread:Plants vs. Zombies Wiki Discussion/@comment-6593079-20130226234600/@comment-5792287-20130402133139

Squash Zombie is the worst Zombotany, not Gatling Pea Zombie. It's fast and very likely to bring down your defenses.

If you've got defenses, even a Gatling Pea Zombie takes ages to bring them down, but a Squash Zombie give the Peashooter and Gatling Pea Zombies an opening.

You can deal with a Squash Zombie by planting something like a Sunflower in their path, but this costs you and you can't always do that if multiple Squash Zombies attack at once.