Question: where to get all the zygarde cells and cores?
Answer: Hau'oli Outskirts: In your room, next to the bed (teaches Extreme Speed)
Iki Town: In Hala's house, in the northeast room (teaches Thousand Arrows)
Konikoni City: Upstairs in Olivia's jewelry shop (teaches Dragon Dance)
Route 17: In the Po Town police department (teaches Thousand Waves)