Not typical to lose drive in both directions all at once. Check the following:
- oil level
- sump screen
- change spin on filter
- linkage from pedals to hydrostatic trans. (Get under and have someone actuate the pedals, you'll see if something is loose/disconnected)
After you have performed the above, do you have steering?
If yes, your pump is good and I would next focus on the charge pressure relief valve. if it is weak/failed/stuck open, you will lose drive.
-If you don't have steering, it is probably your pump.
That should keep you busy for a while, good luck.
P.S. Be certain the change the spin on filter on a regular basis because as designed when the filter clogs it bypasses oil around it right back into the system. This will feed dirty oil into all hydrostatic/hydraulic compoents and wear/fail them prematurely. I would change mine every 6 months. Cheap insurance.