Zazz was a planet the Sixth Doctor visited with Frobisher and Peri to attend a party held by the Lorduke of Zazz. Professor Strut was developing a rocket there to fly to the planet's moon.
Strut accidentally caused a plague of self-replicating robots to infect the planet. The Doctor was able to hustle the robot's into the professor's rocket, taking them to the moon. (COMIC: The Gift)
At some point in its history, Zazz was placed under the protection of the Galactic Heritage. (PROSE: The Tomorrow Windows)