It should hopefully be as simple as connecting the pedelec unit to one motor and then linking the signal wire to the other motor's pedelec connector.
Check out the wiring diagram in
this post which shows how to connect it.
You'll need to make sure that the direction is programmed the same for both motors, or it might activate one motor when pedalling forwards, and the other when pedalling backwards.
Unfortunately, I don't recall dual pedelec ever being tried by anyone on the forum yet, so perhaps you can let use know if it works correctly.
Alan
