As far as I know the mission engineering expression pedal is basically just a 10K passive pot (TIP) with a button to close the RING position
So you would set it up basically like any other expression
If you want them to control at the same time, use MIDI CC XMT (see H9 user manual p.46-48)
If you want to control them individual, may need some kind of switcher/isolator, these products definitely do exist
Good luck
