From QRZ.Com, the Icom handout, and Part 97 Of The FCC Rules -
Ham Radio Glossary - An overview of amateur radio terms.

Zed
A way of saying the letter "Z"; considered by many to be a more precise
way of expressing that letter "Z"; prevents others from confusing "Z"
with "E", "P", etc.

Zulu
Often used to refer to UTC, as in "Zulu Time". See "UTC".
--- SBBSecho 3.20-Win32
* Origin: The Thunderbolt BBS - Little Rock, Arkansas (954:895/7)