Zeb Skip

If you're already familiar with Super Metroid's Zeb Skip, there is a similar concept with a similar result in Zero Mission. The biggest difference for Zero Mission is the trick is much harder and with a smaller return on investment.

There are 4 zebitites in the Mother Brain room, and each one takes 7 missiles to destroy. With the optimal ammo of 50 missiles and 4 supers missiles, you normally would destroy the first two zebitites, go back and refill in the previous room, and then come back with just enough ammo to destroy the last two zebitites and defeat Mother Brain.

If you perform the zeb skip, you don't have to destroy the first one and the third one doesn't spawn, which means you enter the room with max ammo and don't have to refill because you only destroy the 2nd and 4th zebitites.