Find a bowling ball in a Sports shop or elsewhere. Take it to the Maintenance Tunnels (Might be worth taking more than one ball if you have the space.)
Take the red car into the tunnels and take the first left and carry on until you get to the dead end. Kill as few zombies as possible. Exit the car, and start bowling the balls in the areas around you with the highest number of possible zombies to hit and this should be easy.