Embryo's are called fetuses after 8 weeks. The term zygotes is only used right after fertilization before cleavage occurs when the embryo is still a single cell.
It lasts 3-5 days until the zygote divides into a blastocyst.
The "zygote" is called a 'fertilized egg' when it becomes embedded in the wall of the uterus.
the zygote called an embryo whe the fertilized egg start to developed to many cells and became multicellular