i wired the coil of the bi-xenon solenoid in parallel to the highbeam in the assembly - when the high beam is on, the solenoid comes on too...

execution of this wiring could be tricky - you would need a Y-split - the bottom end of Y to go to car connector, one arm of Y to go to solenoid and the other arm to go to high beam... you would need either assemble this Y using correct connectors or, if somebody makes those specific Y-connectors, just buy them...