X Y Z
Zulu time (GMT/UTC), as used in aviation reports, forecasts and more generally by the meteorological fraternity used to military usage. It is gradually being ousted though by UTC (or sometimes just UT).
Zero-degree (celsius) Level. A somewhat better description of this variable than 'freezing' level. (q.v.)
A predominantly west-to-east airflow is termed zonal (and an east-to-west airflow is negative zonal).The strength of the flow in any sector may be expressed in terms of a zonal index given by the difference in average contour height between two latitude circles through the sector.