You can simply start the Distance command, select the first point, select the first point again while holding the cmd key (or, on Windows, the Ctrl key), and then snap to the second point.
Holding cmd will put you in elevator mode.
-wim
Note that the command line report for Distance shows not only the direct linear distance, but also the deltas x, y and z in both CPlane and World coordinate systems. Unfortunately command line reporting on Mac is extremely minimal, so you would need to have the command history inspector open in the right sidebar to see this info. In Windows, if you have 3 command lines showing you see this: