In the second process, the sperm enters the egg, and the zygote is formed.
It’s difficult to imagine more than one process here. I think you mean:
- In the second stage of the process, the sperm enters the egg, and the zygote is formed.
In English a process can occasionally be broken down into sub-processes, but normally we talk about these as stages. Indonesians often make the same mistake with menu and items on a menu:
- The second menu is ayam lalapan.
- The second item on the menu is ayam lalapan.