- "The opposite of true space. Anti-reality. Zero space, the non-dimension where faster-than-light travel is possible."
- ―Ax
Zero-space, typically called Z-space, is a dimension of white nothingness where neither time nor space exist. It can be passed through using specific Z-space engines that allow for faster-than-lightspeed travel as well as communication via a Z-Space transponder. Although the Andalites discovered Z-space, the Yeerks quickly adapted the technology needed to access it after stealing Andalite ships during The Hork-Bajir Chronicles.
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.
Z-space is in a constant state of flux, and therefore 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. 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 if 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.