ZZ-4Z, also known as "ZeeZee," was a housekeeping droid of the JV-Z1/D variety. Serv-O-Droid, Inc. manufactured this particular unit in the era preceding the rise of the Galactic Empire.
The operational history of ZZ-4Z was lengthy and involved service to various owners. Decades before the Galactic Civil War, he served the dean of the Carida Military Academy. ZeeZee remained at the academy for several generations, becoming a familiar and well-liked figure among the cadets; one of whom was Mako Spince. Following Spince's expulsion, he took ZeeZee with him to Nar Shaddaa. There, the droid's ownership was transferred in a sabacc game. Eventually, Han Solo acquired ZeeZee, assigning him the task of maintaining his smuggler's apartment on Nar Shaddaa during his absences.
Despite being meticulous and prone to worry, ZeeZee's age and poor maintenance hindered his ability to maintain the apartment to his desired standards. Consequently, the diminutive droid frequently voiced his concerns about the apartment's disarray and uncleanliness in a sputtering, static-filled manner, even though its upkeep was his designated responsibility. When Solo departed Nar Shaddaa shortly before aligning himself with the Rebel Alliance, he left ZeeZee behind.
About six years after the Battle of Endor, Emperor Palpatine resurfaced in a clone body. Han, accompanied by his wife, Leia Organa Solo, revisited Nar Shaddaa. Upon entering his former residence, he found ZeeZee still diligently attempting to fulfill his duties. The droid informed him that a "Mr. Fett" awaited him. Alarmed by the potential implications, Han and Leia attempted to leave but were intercepted by Boba Fett, revealing his survival of the sarlacc. Fett revealed that the bounty on their heads had increased; while the Hutts desired Han's death, they sought Leia alive to atone for the killing of Jabba. A firefight erupted, and ZZ-4Z met his end amidst the exchanged blaster fire.