zero - fuel weight maximum permissible weight of an aircraft beyond which an additional load must be in the form of fuel (i.e. max take-off weight less total usable fuel in applicable aircraft, which are so limited because of the wing-bending moments associated with near-empty wing fuel tanks).

zero - timed overhauling an aero-engine to 'service limits' (not the same 'good as new' or factory remanufactured).

Zulu or Z - used worldwide for times of flight operations, formerly Greenwich Mean Time, now Co-ordinated Universal Time (UTC)