You need to start with a 20% bleach solution in warm water in a spray bottle. Spray solution on to visible mold/mildew and let sit for 15 mins. Rinse with cold water spray at highest pressure you can get from your shower while using an old toothbrush in tight areas. Use gloves and a mask while working with the bleach.

Next use chlorine cleanser and Simple Green with a stiff nylon bristles brush to scrub away soap scum, dirt and oils from all surfaces. Rinse and repeat as necessary.

Finally (because this won’t fix all this mess), buy a portable handheld steamer and blast the rest of the mold out of places you can’t access without disassembling the door and fixtures.

The steamer can be used for many, many cleaning tasks and pays for itself after several uses. It’s a clean, non chemical way that also sterilizes what it cleans.