ZACK

ZACK is a recursive acronym meaning Zack, Aidan, Cairo, and Kit. It's a catch-all name referring to referring to a variety things both in-universe and real life.

As a Shared Universe
Primarily, ZACK is a Shared Universe that refers to a of variety series. The two major ones involve The Furry Blue DJ 2016 and Furville series with Zack Casey & Bellow, respectively. However despite the name mainly revolving one of the two Zacks, they're plenty of one-off stories or shorts, such as Liem Reed's story with ColleSoft Inc.

As a Team
ZACK also refers Bellow's super powered team. In this case, the recursive acronym is taken literately.