Locating the Zone entrance[edit]
You now possess the Air Helmet and the Jump Shoes which the rest of the zones are all available to you. There really is no best way to proceed. With no clear cut direction, you can simply start over from the front of the house and work your way through it. If you happened to revisit Room A since you collected the Zone Detector, you may have noticed it blinking when you enter and face the North wall. It's easy enough to get to. Return to Room N from hidden room b, climb down the ladder in the wall to Room J, exit and climb down the steps, and walk to the right.
Room A[edit]
You've been here before, and with only one gun on the East wall, it hardly suffices as a good place to replenish your supplies. Before you actually enter Zone 5 from the North wall, it would be a very good idea to visit other rooms to collect guns, grenades, and health potions. Just because you are equipped with an Air Helmet and Jump Shoes does not mean that the trips through the zones will be an easy ride. Get as close to full health before you enter any zone.
Into Zone 5[edit]
Zone 5 is in many ways very similar to Zones 2 and 3. It contains the same makeup of enemies. Slimes occupy most of the floors while bats fly around above the platforms. Disembodied heads fall down from the ceiling and dash across the floor when they reach the bottom. Winged demons make occasional appearances along with a couple of large hopping beasts. Use the same strategies you have employed all along to get past them.
As long as you have the Jump Shoes then it makes relatively little difference whether you choose to take the upper path or the lower path. However, when you approach the small pool of water, you will need to climb down the ladder and jump up to the platform above the pool. If you do not have the Jump Shoes, you will not be able to make it beyond this point. Assuming that you do, you should be able to leap up and over, and continue all the way to the end on the right to challenge the boss.
Boss[edit]
The boss of the fifth zone is a little similar to the boss of the third zone, only it requires more strategy. It is similar because it is forced to occupy the bottom floor, and it has periods of inactivity during which you should attack. However, when it is active, it is quite dangerous, and should be avoided entirely. While active, it spins around, deflecting any kind of attack. In fact, if you shoot a bullet at it, it may bounce back it hit you! Only attack it when it is standing perfectly still.
When it is spinning, it is best to retreat to the upper right corner. The boss will track your horizontal position along the floor. Since you can lead it in any direction, you can usually get it to stop along the right corner of the room. Then you can hop down the right shaft and get a few shots off at it before hopping up onto the ladder and climbing out of danger when it starts spinning again. Do your best to get off the floor once it reawakens. After a few rounds of this, you should have it defeated. You can pick up the health capsule that extends your life at any time. Make your way carefully back to the zone entrance after you have collected the fifth laser gun piece.