Answer:
Pre-zygotic factors; post-zygotic factors
Explanation:
Fertilization is the process of fusion of male gamete (sperm) and female gamete (egg). Before fertilization, all the events are known as pre-fertilization events and those which occurs after fertilization are known as post-fertilization events.
There are various factors which help in fertilization. All species contain some receptors on the membrane of egg which play very important role in fertilization and prevent fertilization between inter-species.
The mating in which the formation of zygote is occurs but it is unable to form a viable embryo, is due to the result of post-zygotic factors.