The swamp zombies are smarter than other zombies. They will protect their heads with their arms. Use your hand gun on their legs when they are at a good distance. Alternately, just blow their legs off with the shotgun.
Tap and hold the ammo clip with the stylus, then tap and hold the left corner where the ammunition is supposed to be dropped with your finger. Lift up the stylus and the ammo clip will instantly appear where your finger is held on the touch screen. Lift up your finger and to reload:
-When you reach the tunnels, use the crowbar on the zombies instead of your guns. When you reach the part in the tunnels when the bats fly at you, use your hand gun on them. After that, use a combination of your shotgun and hand gun on the zombies. If you can do this successfully, you can finally get out of the tunnels and out of the chapter. There will be more zombies outside the tunnels for awhile; be ready for them.
-To kill the shambling zombies that cover their faces, use the shotgun. Fire a shot to their ankles to kill them. Note: This only work when they are standing fully upright.