What happens to a zygote after it forms and begins to develop

In humans, it takes about four days for a zygote to become a  morula  and another three days until the embryo attaches itself to the mother's uterine wall.

both male and female gametes are produced by meiosis of the germ cells. therefore, both male and female gametes are haploid. one male and one female gamete unite during the fertilization to form the diploid zygote. in seed bearing plants, pollen grain is the male gametophyte, which produces sperm cells.