Relatively easy to achieve. You can get to the power room by taking the elevator at the start of the level and jumping a gap after the corridor where the elevator falls. It will cost you 750 to open the door to the power room. As you work your way down towards the power room, you will find the parts around that general area. It might take a few waves to gather enough points to open the doors surrounding the power room in order to find the parts for the wonder weapon. Once you have the gun built, just shoot the center mass of a zombie and he will explode, and as long as there are zombies around him, the goo on the ground will take care of them. Note that this will only work on zombies that do not have body armor, as it goes through them, and in later waves the normal zombies will most likely slip instead of die, as they did in my game in the later waves.
Also, in case some need help finding the parts, there is a video below to help out.