Zen was the master control computer of the Liberator, responsible for the majority of ship operations.
Zen's fascia was located on the Liberator flight deck. It was capable of verbal interaction with the crew once it had assimilated their language and could fly the ship unassisted. As all the subsystems of the ship were controlled by other computers which were in turn controlled by Zen, even when the ship was theoretically under manual control Zen was still involved in its operation. Zen also had a sizable database of astrographic and general planetary information.
Once the Liberator defence system had been destroyed, Zen accepted orders from Blake, Avon and Jenna unquestioningly. At a later date further safeguards were introduced with the computer only responding to commands from recognised crew members. Even without voice-print authorisation, it was possible for a trained crew to operate the ship without Zen's involvement. Zen's initial programming occasionally made it less than completely helpful.
As Orac was capable of taking control of Zen, it seems almost certain that either tarial cells or a close analogue were involved in its construction. Avon described it as a capacity-charged brain without going into further detail. Blake and the rest of the crew tended to treat Zen as an individual with its own personality, somewhat to Avon's disgust - in his view, Zen [was] a machine.
Zen made itself known to Blake and his followers shortly after they boarded and destroyed the defence system. The name Liberator was first used by Zen after extracting it from Jenna's mind when she touched the controls.
While generally helpful, Zen's directives occasionally conflicted with the needs of the crew. Even when questioned it remained silent about the origins and builders of the Liberator. It also announced that it was forbidden to interfere with crew activities, even when they included the sabotage of the ship, and refused (with no reason given) to take on board the capsule discovered en route to Saurian Major. Zen was also at least initially incapable of accepting an order which it believed would cause its own destruction, temporarily shutting down itself and all the other on-board computers.
Following the recapture of the Liberator by the System, which was in part made possible by the System's access to Zen's programming, Avon made Orac reprogram it. Following this Zen was generally more co-operative.
Along with the rest of the ship, Zen suffered rapid failure when the Liberator became contaminated with fluidic particles en route to Terminal, displaying signs of distress and regret, as well as referring to itself as 'I' for the first and only time. It was destroyed when the ship broke up over Terminal. His last words were I have failed you, I am sorry, I have--. (C: Terminal)