1) Zero point of change 
ZPC (Zero Population Count) is a first-person shooter computer game developed by Zombie LLC in 1996 which uses the Marathon 2 engine. It was noted for its stylized look adapted from artwork by Aidan Hughes (also credited with the game`s concept). The story focuses on Arman, an exiled `Warrior Messiah` who has come of age and sets out to reclaim......
(Aviation abbreviations:) zone power converter
acronym: zero point of change (hydrous iron and aluminum oxides)