If your Zygarde has higher attack power:
-Dragon Dance
-Extreme Speed
-Earthquake
-Dragon Tail/Outrage
If it has better defense:
-Coil
-Stone Edge
-Earthquake
-Dragon Tail/Outrage
You can also swap out the first two moves for Rest and Sleep Talk, but that's a bit slower to pull off.
Just don't expect Zygarde to perform as well as Garchomp or Dragonite: Its stats are a bit too low for it to sweep like they do.