Let the world know that if you would like to solder the optional 3.5mm jack onto this board, the correct orientation is over the board, as with the RCA jacks.
I have asked support. Amazed support did not know the correct orientation.
I tried to follow the traces, looked at other HiFiBerry boards with the 3.5mm jack, looked at pin documentations. All that research seemed to suggest it was supposed to be mounted under the board.
Apparently not. After realizing I was hearing opposite channels, I tried to desolder and ended up destroying that section on my unit.
Again, the correct orientation to mount the 3.5mm jack is over the board, as with the RCA jacks.
My Friday is ruined, my OCD nerves hates my DAC+ Zero now. I hope the support team reads this and document for other newbs like me.