Zar was an alien con artist who impersonated Starfleet Commander Chakotay in 2376.
Using this deception, he and his partners Dala and Mobar were able to move from star system to star system offering services for different goods from the various races, but not delivering what they promised. Eventually, USS Voyager caught up with the three and captured them, returning everything they had stolen. (VOY: "Live Fast and Prosper")
Zar was played by Francis Guinan.
The name Zar originated from the source's script.