The letter Z is unusual because it has three names. It is named Zed, with a short E, in England, Canada, Australia and New Zealand. In America the letter is Zee, with a long E. Brits and Canadians are fond of pointing out that they, unlike the Americans, use the correct name. In Hong Kong the same letter is pronounced Eezed, with both a short E and a long E. The trouble is that all three names were in use in England historically, with Zed being specifically Norman and upper class. There are even some old variants of Zed that are no longer in use. These include Zad, Zard, Izzard, Ezod and Uzzard.
Hong Kong's Eezed is not wrong and was one of the names for Z used in British English until about 400 years ago. However it can cause confusion today: One day my principal spelled the name of a new student in my class. I wrote down, S E Z E. Then she said, "No her name is spelled S E Z E." It turned out that the girl's name was Sze. To be sure of being understood use Zed or Zee.
The name of the letter Z is used more than the names of other ordinary letters. It is commonly used as an unknown variable in algebra and the z-axis in geometry. In physics Z can be written instead of the atomic number of an element.
Things might be described as having a Z-shape, such as a Z-fold in printed paper. The word ZZZZZZZZZ is used in English language comics to represent the sound of a person snoring (French comics more often use RRRRR or "Rron"). Even the sleeping emoji uses Z in this way. The phrase, to catch some Z's is an idiom (in US English) for going to sleep. Other special Z-shaped words include the Z-bar (a metal bar having a Z-shaped cross-section) and the Z-bend (a series of bends in a road with a Z-shape).
Many children's TV programs, such as Sesame Street, have consistently used the Zee name for Zed. As a result, even in the UK, Zee is on the rise over Zed. However since they are both historically correct, this change should not be a problem.