The Ra Zombie will bite the plant in its lane as its regular attack and use its staff to damage all plants in the lane it is in as its special attack. However considering that both attacks are weak, with its low health, the player should have no problems defeating it.
You should place a defensive plant, such as a Wall-nut in the middle, as this the lane where Ra Zombie is at. Use it as a stall to let your offensive plants attack the zombie.
Mummy Zombie x2
Ra Zombie (Leader)