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)