Is that Pro2's rther than Pro3's – coopersport1 has said the Pro3's are screwed in.
Answer for Pro3 (Pro III) Hubs is to unscrew them – there's a threaded end to the QR adapters. One of the adapters goes all the way through the middle of the Hub and screws into the shorter adapter at the other side.
Appears they're maybe glued together as they're REALLY tight.
So to unscrew the simplest thing is two Allen keys, one each side, and apply loads of force. Hope response was 'swing on them – they'll be fine' so there we are. I couldn't do it using a screwdriver with allen key head on one side and allen key in the other – too much give in the arm using the screwdriver. Two Allen keys though, preferably not in a flexible tool tyoe mount so you get maximum purchase and eventually the glue gives with a small 'crack' and job done. 15Qr straight in and we're off.
Cheers coopersport1 for the screw in tip !!