To interact with Zoroark you will need either:
- Event Raikou
- Event Entei
- Event Suicune
They are obtained through a 13th movie event. Normal Raikou, Entei or Suicune will not activate Zoroark's appearance. The Raikou, Entei and Suicune obtained from this event are always shiny.
If you have them, you can go to Lostlorn Forest and encounter Zoroark.
Hope I helped. :)