Shuji at Zwift HQ here. Some people use the rubber O-rings to attach Click v2 controllers to the outside of the shift levers. If you spend more of your time on the drop bars, that might be handy.
If you spend more time on your aero bars, you might consider the 3D printed adapters that attach the to end of the aero extensions.
If your answer is “I want both options” - you can pair up to two sets of controllers to Zwift at the same time.