I know this was answered but I want a more recent answer just in case. Is Zygarde shiny locked??
It is shiny locked in both X and Y and ORAS which means that it can't be legally shiny ingame. I am damn sure for XY but not for ORAS. There is like an 85% chance that I am right.
I know you asked this when Gen 7 didn't release, but we will be able to get Shiny Zygrade from the event of the legendary Pokemon year in June.
So, Zygrade won't be shiny locked in June.