The events of the episode reveal that Zural actually acted as a double agent for both the Cat race and the Brefewino, and had betrayed his own people.
Zural was born aboard Red Dwarf, possibly in Supply Pipe 28, and later left along with all the able-bodied Cats on one of the Cat Arks - Zural was fortunate enough to be in the one which didn't crash into an asteroid. The Cats formed a military structure, likely to fend off attack from the Brefewino, and Zural became a trusted platoon commander. One of the female Cat soldiers under his command was Ora Panzil, sub-lieutenant 2960B8651.
The platoon was betrayed by persons and for reasons unknown, with some of them being killed, some eaten, and others enslaved for auction by the Brefewino. Ora was taken to a Brefewino planet.
Zural used a morphing belt to pretend to be "Zurool", a male Brefewino, and infiltrate the Brefewino town. Knowing an attempted jail-break would likely be suicide, Zural instead decided on buying Ora himself at auction as one of the Brefewino.
Events of Identity Within
Under this Brefewino guise, Zural stopped his potential competition the Cat from freeing Ora himself from the cage she was in. Zural later watched, knowingly, as Dave Lister attempted to use Kryten to cheat at four-dimensional pontoon in a gambling watunga - but Zural cut in at the winning hand, winning all the mushy peas to buy Ora with, and even the keys to Starbug.
However, Zural's true intentions for when he had freed Ora were not so noble. Before he was able to kill a freed Ora, Zural was instead killed by the Cat, who then revealed Zural's treachery by showing the knife hidden behind his back - his Cat instincts about Zural had been right.
Ora says that Zural must have been the one who betrayed the rest their platoon to the Brefewino, perhaps to save his own skin, or for profit, and Zural didn't want Ora figuring it out, or exposing him, and so wanted her dead and not a slave. The competition removed, Cat was then able to mate with Ora, saving his life from a libido-related illness. ("Identity Within")