I want that big black greninja
There are multiple ways for shiny hunting in Legends Z-A . You could choose between the fly spam method, the bench rest method, or even running back and forth to make whichever Pokemon you desire to be shiny despawn and respawn with a chance of being shiny . Either of these methods could work because Z-A locks the Pokemon the moment its a shiny, so it wont despawn once you find a shiny .