M (mining) and Z (waste dump) show the exact same areas

Since they both show the same marked areas it is quiet easy to confuse a mineable area with a dump area. M and Z should definitely only show mining or dump areas. Not both at the same time.

I disagree. They are differently colored. You WANT to see both at the same time to avoid conflicts, like dumping just above mining area, creating an infinite loop when the loose dump starts pouring down on the excavator

I agree with Ray. If, on the other hand, there was a menu on the left like L to select which areas to display/manage at a given time, that could be helpful and then the M key could take over for both potentially.