|Episode(s)||15.15 Gimme Shelter|
Zack is summoned by Castiel, who wishes to find out if demons are involved in a series of murders. Zack tells Cas and Jack that it is not the work of demons, though he appreciates the work, and reveals that Rowena has disallowed demons to make deals with humans, believing that "people end up where they belong." Due his boredom in not being able to make deals, he becomes intrigued that Castiel and Jack are investigating human murders and begs to come along, offering to be their driver, but he is soundly rebuffed.
As Sylvia is being placed in a police car, Zack appears as a deputy, flashing his red demon eyes as he looks back at Sylvia.