Heat the back cover of your Xperia Z3 to loosen the adhesive underneath.

If you use an iOpener, follow these instructions for use.

Lift up the back cover with a suction handle and put an opening pick in the gap.

Move the pick carefully around the edges to loosen the adhesive on every side of the phone.

Don't put the pick in too deep under the back cover to not damage any parts inside the phone.