Here is how I used to unhook/hook up hydraulic couples be it right or wrong.
If the implement has a transport lock, engage it or let implement down to rest on the ground, then shut tractor engine off and work remote lever fwd/rev until all pressure is off the hydraulic lines, then unhook the hydraulic couplers.
To hook up:
Again turn tractor off and work remote lever fwd/rev to release pressure on hydraulic lines then connect hydraulic couplers.
I don"t know if this method will work on closed center hydraulic system but works on open center system.