Zombie Storage is a glitch that causes up to three Links to move as corpse while the other(s) are still alive.
You want to get GBA OoB and then die as Green Link as the others are still out of bounds. This will store the death of the others. Now reunite and die again (as Green Link! Otherwise you will control a Zombie and cannot do much). By that you will activate the "Zombie mode", causing only Green Link to revive, while the others are dead, but can still move around. Now, as you die another time, the Zombies are actually able to move through certain objects while Green dies. Valid objects are: Flames like in Kakariko, the electric beams in the Barrier at the end of each level, Barriers like the one in 1-3 and Snow walls like in 7-1.
So far, only successful bypassings of flames have been recorded, as well as bypassing the gem barrier in 2-1, which is completely useless.
Useful example is the Kakariko Sequence Break:
Note: This method was replaced by a faster one, check the World 5 article .
Dying on staircases that load a new area can cause Zombie Storage as well. A special side effect though is that when you trigger the Storage (ergo dying again), Green actually does not die while the others become corpses (Sometimes they don't). You also dont lose a Force Fairy. Additionaly, you will most likely respawn where you entered the screen.
Warning: Dying on staircases can also cause a softlock, depending on your position when you die! Video someday.
Another technique that uses the effect of Zombies.
In this case, you (somehow) get Zombies into a solid object. This makes them able to move through any solid object that is connected to the initial one. Exiting the solid tiles lets them return to the normal ones, but they cannot go back then. To be able to transition screens, you need to die to remove the Zombie State. Any zombies that are inside an object as they revive will respawn next to Green.
The easiest way to accomplish Zombie Clipping is moving Zombies over a Bombflower. Due to the different hitbox of the Zombies, bombs will regrow even when you are on top of them, making you clip immediately. Another way to acccomplish this trick is abusing screen transitions to get non Green Links oscillating in walls and then die as Green.