The latin letter z is used to represent a variable or coefficient. The symbol z is also used to represent the up/down dimension in the 3D cartesian coordinate system.
The Latin Alphabet is a collection of 26 symbols that form the basis of the English language. The alphabet's symbols are used throughout mathematics to represent variables, constants, and coeffecients.
The capital Latin letter Z is used in mathematics to represent the set of integers. Usually, the letter is presented with a "double-struck" typeface to indicate that it is the set of integers.