Use the edge of a spudger to pry up the flap of the ZIF connector located below the SIM slot on the left side of the motherboard.

Use a pair of tweezers to pull the power and volume button flex cable out of the ZIF connector.

To reattach ZIF connectors like this one, carefully insert the flex cable into the ZIF connector up to the marked line on the cable, and then close the locking flap.