With Machamp's muscles available to you, it's high time we checked out those places earlier with the big cube-shaped boulders. Of course, since it's been such a long time and so many things have happened, it's easy to forget where they were. Thankfully, we've been keeping tabs.
Ten Carat Hill
Call Charizard using your Ride Pager and wing your way to Route 1 - Hau'oli Outskirts on Melemele Island. You'll be taken right outside the entrance of Ten Carat Hill, which is where you're heading first.
Inside, make your way to the far west of the cave, smashing through the rocks along the way with Tauros. Before the entrance to the Farthest Hollow, there's a giant cube in the south-west corner. Have Machamp push it forward into the nearby gap in the floor.
Cross over and carry on west. Eventually you'll need to go on foot along a narrow path by the side of the subterranean stream. At the end of this path is an exit to the south-west corner of the Farthest Hollow. Beyond, inspect the pedestal to receive Flyinium Z.
From here, you can glide to the next location.
Starting from the main entrance, make your way to the east zone, where the breakable rocks are. In the north-east corner is another cube that you can push. Approach the cube from its north side and let Machamp shove it south into the gap.
Across the gap, there's an exit immediately to the east. On the other side, you'll emerge in a small tunnel. Carry on east. In the corner up ahead, just below the pile of rocks is a Zygade Cell (27), the final one on Akala Island.
Nearby is another giant cube. Kindly ask Machamp to shove it east, until it's below a gap in the floor. After that, go around to the south side of the cube and shove it north into the gap. If you messed it up, you can exit the cave and re-enter to restore it to its original position.
South from here is an Awakening sitting in the corner by a small rock. Meanwhile, if you search around the pile of rocks to the east, you can find a buried Rare Candy. Finally, head north from the sunken cube to exit. You'll arrive back on Route 8; nearby is TM53 Energy Ball.
Make your way to the west-most side of Diglett's Tunnel, about halfway up. If you need directions, start from the south entrance and go west. When you reach the lone trough along the north, follow the narrow path leading south. Run past the burrowing Pokemon circling around.
Beyond here, you'll find the large cube you're looking for towards the north, west from the Worker. Summon Machamp and shove the cube west into the gap in the floor. As usual, head across the cube after it drops into the gap and follow the remainder of the path north.
Past the exit, you'll emerge in Konikoni City, east from the Lighthouse Point. Go around and up the nearby slope. Before continuing on, search the outcrop to the east of the slope for a Big Pearl. Finally, go west to find TM61 Will-O-Wisp by the side of the lighthouse.
Sadly you can't enter the lighthouse itself and the way back to the rest of Konikoni City is barred. So you should call Charizard to carry you back to a safe place.