From the first screen of the Desert,
- go east to find a Max Elixir, then go west to previous screen
- go north then north again, talk to the hiker at night time to get the Safety Goggles, then go south (once) to previous screen
- go east to find a Zygarde cell in the center of the screen, there is also a man who wants to see a Lunatone or Solrock in your party
- go north then east to find the Psychium Z-Crystal on the far right side of the screen
- go west to find a Comet Shard in the middle of the rocky Mudsdale terrain
- go south to find the Dream Eater TM at the bottom of the screen
from there you can go north then north again to reach the Ruins of Abundance, or just use Charizard to fly out.
This walkthrough has a map of the Haina Desert, but their path doesn't include the hiker who gives Safety Goggles.