Hover over the icons under "Damage" to see list of attacks.
Strategy: Take a strong Armadillo Dragon with Asteroid attack, or take a strong plant dragon, like a Tropical, against the Pirate. A strong Neon or Gummy (with Tesla Ray) against the Zombie will deal great damage and provide good resistance. To beat the Poo dragon, a strong Pearl or Soccer Dragon will do the trick. Or, you can just take a level 18 Pure anything and defeat all three with just the one dragon.