Nexus Zero is a location associated with the Vok, presumably their home. It doesn't seem to be a planet, but rather a nebulous cloud where the Vok float around, talk, and keep their kidnap victims in stasis.
There are other nexi, all part of a wormhole network facilitating travel across the galaxy. The only other specific one known is Nexus Earth, but that pathway was destroyed by the Metal Hunter's explosion. Because of this, Tigerhawk would be sent to Earth via a comet-like vessel instead.
Beast Wars cartoon
After interrogating Optimus Primal on Earth, the Vok decided to sterilize the planet, activating the Planet Buster. When the Planet Buster was operational, they declared, "Termination sequence engaged. Return to Nexus Zero," at which point they vanished from the Earth in a streak of light.
Tigatron and Airazor were later captured by a giant plant and "beamed" off the planet in a similar fashion. serious disruption in the timeflow, location: Nexus Earth." Others were skeptical, as "that nexus has been closed; the experiment has been terminated." In the end, they decided to merge Tigatron and Airazor into Tigerhawk and send him to Earth as their emissary to capture or destroy Megatron, who had caused the timestorm.They ended up at Nexus Zero, where the Vok held them in some kind of stasis. Some time afterwards, a debate emerged among the Vok: Some were concerned about "a
- Larry DiTillio intended Nexus Zero (which he called the Vok Nebula) to be one and the same with the Matrix Dimension, the source and destination of Transformer sparks. However, this idea never made it into the show, and it was eventually supplanted by the Allspark.