Update August 9th, 2021: Video updated to include steps for entering maintenance mode prior to starting work on the rear brakes, and for exiting maintenance mode after completion of all rear brake work.

This video walks through my experience with changing the rear brake pads on a 2018 Mazda3 (equipped with the electronic parking brake). Spoiler - I went a little over on miles, and should have changed these pads a few months sooner, in order to prevent some minor damage to my rotors. I got just over 26,000 miles on these pads, and they probably should have been replaced at 25,000 if I'm guessing.

This was my first experience changing the pads on this vehicle, and I hadn't done any research ahead of time. Next time I'll check the literature for applying grease to the caliper pins, and if it's recommended to lubricate any other areas. I'm not a certified mechanic, so learn from my mistakes, but don't take my path as gospel, by any means. I didn't see any videos out there for 2018 Mazda3 brake pad replacement, so until someone does better, I hope this helps a little bit. The worst part by far was dealing with the compression on the piston, other than that it was a pretty straight forward experience.

Additional August 9th thoughts: Now I'm curious (if you use Maintenance mode, does that remove the difficulty I had in retracting my pistons? I'll find out next time I guess, but I suspect this will make a big difference (much easier I hope). You can hear the piston compressing for a while, either this means it is compressed in a useful way, or it likely means it took the load off the piston, and maybe it's easier to compress. Please comment if you beat me to it, I'd really like to know for next time.

Special thanks to user "Line Lauzon" for the helpful comment.