"Nope! I know who I know... and who I don't know. And I DON'T know her." - Zuben, after being questioned about Lucy
Military Service and Family
Zuben was part of an all-replicant Off-world combat unit called Lightning Squad that fought in the Battle of the Gemini prior to his involvement in the Moonbus hijacking. He is one of the perpetrators of the animal murder case at Runciter's that begins the story of the game.
Events of 2019
Ray McCoy's investigation
McCoy's investigation at Runciter's reveals clues indicating two suspects, one large and hobbling suspect and the other with a long, almost graceful gait (Zuben and Clovis, respectively). Other clues found near Lucy's desk reveals a Howie Lee's receipt, prompting McCoy to take his investigation to Chinatown.
When Ray McCoy arrives at Howie Lee's, Lee tells him that Zuben is a new chef that has only worked for him for a couple of months. McCoy goes out back to interrogate Zuben about Lucy, and the latter ends up attempting to escape. Before he flees, he dumps soup on McCoy in an attempt to slow him down.
(McCoy can either dodge the soup by clicking quickly to the right before Zuben is able to finish, or fail to react in time and get slowed down as Zuben makes his escape.)
Retirement or Escape
McCoy chases after Zuben, making his way through the back alley and into an abandoned warehouse, finally reaching a hallway with a locked door. Zuben, if he ran and McCoy was not fast enough, or refuses to chase him altogether, will not be here. If McCoy was quick enough, Zuben will jump down from the ceiling and approach McCoy with a butcher's knife. At this point, McCoy has the choice to shoot and retire Zuben or put his gun away and let Zuben go.
Alternatively, if not chased down in the back alleys, McCoy will be ambushed by Zuben the next time he returns to his apartment. The same choice is offered here: shoot Zuben or let him go.
If shot at either location, you can pick up his war photo from his corpse.