Why do other countries say Zed?
In most English-speaking countries, including Australia, Canada, India, Ireland, New Zealand and the United Kingdom, the letter’s name is zed /zɛd/, reflecting its derivation from the Greek zeta (this dates to Latin, which borrowed X, Y, and Z from Greek, along with their names), but in American English its name is zee
Why do the British say zed instead of zee?
The British and others pronounce “z”, “zed”, owing to the origin of the letter “z”, the Greek letter “Zeta”. This gave rise to the Old French “zede”, which resulted in the English “zed” around the 15th century.