Its program was modified to facilitate extra-dimensional activities, but that led to noticeably strange behavior. Additional software was installed to make it a better Pokémon. It began acting oddly, however. Its programming was modified to enable it to travel through alien dimensions. Seems there might have been an error...
Pokédex entry #474
Porygon-z is a type normal Pokémon that evolves from porygon and porygon2.
Porygon-z in Pokémon GO
It's possible to hatch Porygon-z from an egg?
No, Porygon-z can't be hatched.
Which are Porygon-z’s strengths and weaknesses?
Porygon-z is a normal type Pokémon. normal type pokémons but weak against rock pokémons. They are not affected by ghost type pokémons.