That’s great thank youNice tractor!
If you have a PTO lever with 3 positions, than one position is the PTO on engine speed, middle position is PTO in neutral, and one position is PTO on ground speed through the gearbox.
I think if you put the High / Low in neutral, and the gear in reverse, than your PTO runs in reverse. Nice for un-doing a stuck post auger.
You don't have to put the lever in neutral if you don't use the PTO, but you can.
On certain models Zetor tractors the PTO lever also has a position that disengages the hydraulic pump.
If you Google "Zetor Proxima owners manual" you will find some. Look for WWW.cals.cz