Who are the "Zools" in the novel, Ambassador of the Shadows?

The Zools are a group of aliens who do most of the maintenance work on Point Central. They are symbolic of the public watchdogs who have the right to protect their way of life. As the novel comes to a close, they embark on a mission to clean up the profiteers and corrupt people on Point Central, arresting some and banishing Earth from Point Central for the next 100 years.