The ZR button can be removed once the red circled screws are removed.

The R button is underneath the ZR button and is easily removed once the ZR button is out of the way. There is a small hole that one end of the R button fits into.

Remove three PH0 screws, two that hold the ZR button plastics and one on the top main board.

The processor for the controller can be seen on the top main board. See the details in Step 9??

The connector between the top and bottom boards is shown here.

The bottom board on the right controller is small and only picks up the bottom three buttons which using a small 6 pin connector.

Warning: Do not try to remove the top main board before you remove this small button board in the next step.