Welcome aboard. 👍
The hi/low beam has been discussed ad nauseam. It helps to know that the Z has the same single filament lamp in each side. To get the high or low beam the housing has two different reflectors, one that throws the beam high and one that throws the beam low.
I suppose the easiest way to have both running at the same time would be to find the wires for the 'passing' switch and adding another switch to shunt them together.