Differentiate between 'ZZ' and 'XY' type of sex-determination mechanisms.

ZZ sex-determination XY sex determination
In this type of chromosomal sex determination mechanism, the females are heterogametic, that is, they produce two types of gametes, while the males are homogametic. In this type of chromosomal sex determination mechanism, the males are heterogametic, that is, they produce two types of gametes, while the females are homogametic.
Here, the females produce two types of eggs (A+Z) and (A+W), while the males produce only one type of sperm (A+Z). Here, the males have an X chromosome and its counterpart Y chromosome, which is distinctly smaller. Hence, the males are XY. However, females have a pair of X chromosomes; therefore, they are XX.
For example, birds, fishes, some reptiles, etc. For example, human and Drosophila.