After you go through Route 11 and pass through the captain's barricade, you go east to Route 12.
Explore Route 12
Go east to route 12. Hapu arrives and registers Mudsdale in your Ride Pager.
Go east and ride Mudsdale across the rocky ground.
Near the upper-right corner of the rocky ground, there is a Burn Heal.
Near that, there is a green sparkle for the Zygarde Cube.
To the east, there is another area of rocky ground. You can go south on the rocks to find a patch of grass. There is a narrow passage at the south end of that grass. After going through that narrow passage, you can go southwest to battle Rising Star Leilani, who has a level 30 Tirtouga. You get 1440 Pokédollars for winning.
South of Leilani, there is an Elixir.
Go east from Leilani, through another narrow passage, and you can battle Punk Pair Yoko and Lane. They have a level 29 Krokorok and a level 29 Pancham. You get 1856 Pokédollars for winning.
South of the Punk Pair, there is a green sparkle for the Zygarde Cube.
Go south, crossing some rocky ground with Mudsdale, and you can battle Rising Star Matthew. He has a level 30 Cranidos. You get 1440 Pokédollars for winning.
East of Matthew, there is a Hyper Potion.
There is more rocky ground south of Matthew. After you go across, go south and you find some grass. Walking around this grass, you can battle Scientist Jayson. He has a level 28 Porygon and a level 29 Magneton. You get 1392 Pokédollars for winning.
Within this circle of grass, on the right side, there is an X Attack.
From here, you can go west for a brief trip to Blush Mountain.
Near the entrance of the area, you can battle Office Worker Shane. He has a level 29 Psyduck and a level 30 Fearow. You get 1200 Pokédollars for winning.
In the grass behind Shane, there is a hidden Zinc.
North of Shane, there is a green sparkle for the Zygarde Cube.
To the west, there is a red truck. There is a Timer Ball behind it.
The fence behind the truck is a Poké Finder spot.
Southwest of the truck, there is a Sun Stone below the grass.
Inside of the Geothermal Power Plant building, there is a Scientist who might say that he will give you something if you come back on another day, so keep him in mind.
Talk to the guy in the bottom-left corner to get a Lure Ball.
Back to Route 12
Now leave the power plant building and go southeast to return to Route 12.
To the left, there is some rocky ground and some grass. You can go over the rocky ground if you want to avoid battles in the grass.
From here, there is a ramp to the southeast that goes down to Secluded Shore, but before you go, there is a hidden PP Up to the left of the ramp, past the grass.
Then you can go down the ramp to Secluded Shore.
To the right of where you entered the Secluded Shore, there is a green sparkle for the Zygarde Cube.
At the far right of the beach, there are some berries under the tree.
South of the tree, there is a hidden Big Pearl.
There is a police officer to the left. North of the officer, there is a hidden Pearl.
To the left, you can battle Swimmer Sara. She has a level 30 Alomomola. You get 720 Pokédollars for winning.
To the left of Sara, there is a hidden Pearl.
To the left of that, you can battle Swimmer Robert. He has a level 29 Whiscash and a level 30 Sandygast. You get 720 Pokédollars for winning.
To the left of the rock near Robert, there is a hidden Big Pearl.
On the far left side of Secluded Shore's beach, there is another green sparkle for the Zygarde Cube.
There are no items or trainers in the water of Secluded Shore, so you can return to Route 12 when you are ready, then go west to reach Route 13.
When you go into Route 13, Hau arrives and gives you a Max Potion. Gladion appears and warns you to keep Cosmog safe from Team Skull.
Go to the left of the motel to find an oasis. There is a Moon Stone to the right of the water.
To the north, there is Haina Desert, but it is blocked by a captain's barricade right now. The old man southeast of the barricade will tell you that if you want to get through the maze in Haina Desert, look at the stone stacks. He says the answer is 2-1-4-3.
In the trailer to the left of the path to Haina Desert, there is a Punk Guy who asks if you want to battle. If you say yes, he gives you TM12 Taunt, but doesn't actually battle you.
South of the oasis, there is a green sparkle for the Zygarde Cube.
Farther south, there is a ledge where you can do some fishing. There is a Guard Spec. on the right side of that ledge.
Go west to reach Tapu Village.