1. To lock up the mall to keep zombies from getting in, you need to park the trucks over the entrances. Get the key from the office on the 2nd floor and go to the 4th floor where the keys to the trucks are kept.
2. To keep the dead zombies from coming to un-life, lock them up in the freezer in the basement.
3. before you can go play in the basement, you need a source of light. Get the fuses and gloves from the 3rd floor and go to it!

First get Alex to drop the helicopter keys by the helicopter. There's no point in carrying them around with you as you won't need them until the very end when you return to the helicopter and it'll enable you to carry around one more useful object in the meantime.

Choose one of the characters and go down to the security room on the second floor, pick up the set of keys and make your way to the list, don't bother getting any weapons and don't stop to kill any zombies.

Use the keys and now you'll be able to go up to the fourth floor (drop the keys in the elevator, you don't need them anymore). Leave the elevator and you'll now be in the main control room, and here you'll find three different keys on the floor, each one of the three will start one of the trucks, enabling you to move them.

Make your way back down to first floor using the elevator. Go to each of the trucks and using the keys, move them in front of the various entrances to the shopping center. The only problem now is that your character will not be able to get back inside. Choose another one of characters and send that character own to the sports shop on the third floor. Get the rope and then go to the balcony above the front entrance on level two. Use the rope and your other character will climb up and onto the balcony away from danger. Have one of your characters get the fuse, the rubber glove, and a gun. Have another character get the torch. Take them in the elevator to the basement and get the character with the torch to use it so that when you exit the elevator you'll be able to see where you are.

Both characters should go around to the fuse box and after you've disposed of any zombies, get the character with the rubber glove to use it and insert the fuse into the fuse box. Now using yet another character, go to the forth floor and press the buttons on the computer to activate the lights in the basement. This is where Operation Zombie Kill starts. Get one of the characters to go around to each of the levels destroying all the zombies that he meets. Stick all of the zombies in the cold storage (if you use the tape from the video shop with the TV and video in the rental shop you'll see that you have to shoot the zombies in the head to kill them). If you now go down to the main entrance you'll see that some thugs have moved the truck and have made their way inside.

Go outside and go to the right after getting the fuel can (level three), a gun (level two), and the hose pipe (level one). You'll soon come across a van belonging to the thugs. Shoot any thugs by the van, and then drop the fuel can in front of it. Now use the hose pipe and, voila! You now have the precious fuel you need to fly away in the helicopter. Get everybody inside the helicopter and start it up with the key, which you left near the helicopter at the beginning of the game, and the game is completed.