Actually, it's stated that shadow pokemon cannot breed. Also, you
could try shiny hunting, but you need to purchase a pokeradar at
the Emera Mall for 150k pd
The egg could hatch Shiny, but it will impossible to hatch as
Shadow. This applies to every egg received from the Daycare,
regardless of what the parents could consist of. Having Shiny
Pokémon as parents for breeding doesn't increase the likelihood of
hatching a Shiny either.