A few things to note. Zombie Panic currently is back on the table of redevelopment. It has been years since a serious update was pushed. There are a lot of glitches and issues while in game play which may appear as if a player is hacking. However, with that being said, the converse logic is true, (Zombielle is correct) VAC and other plugins for ZPS may have issues (again because of being outdated).
I will look over this information and get back to both parties before making a ruling.