- "The opposite of true space. Anti-reality. Zero space, the non-dimension where faster-than-light travel is possible."
Z-space is important in morphing because it essentially serves as a reservoir for matter used during the morphing process. Excess matter is held in Z-space when someone morphs a creature smaller than their regular body, and extra matter is retrieved from Z-space when someone morphs a creature larger than their regular body and more mass is needed. It was once thought that matter clumped there in its basic elements, but was later discovered that the morpher is kept in their regular form plus or minus whatever matter was added or taken away for the morph being used.
It is important to note that Z-space is in a constant state of flux. A route through Z-space that takes one day to travel through at present moment may later take a month or ten years to travel though. This is why the Andalite fleet cannot arrive quickly despite having been informed of Earth’s invasion. In addition, there is an astronomically small probability that a ship flying through Z-space will collide with the mass of a morph. Generally, the being will be killed due to the mass and speed of the ship. Survival is possible is the being is caught in the wake of the ship; however, Z-space is not conducive to life and a being would die unless rescued.