It's possible, but desn't make any sense at all. These motors have the advantage that they're small, lightweight and can produce a lot of torque with relatively low power by allowing the bike to run more slowly than a normal motor. Two Q128s would be the same weight, but would blitz a pair of Xiongdas in a climbing contest. A single Mac would be lighter and a lot simpler.
if you want to run with two Xiongdas, you'll need to install two LCDs and have two control panels, which will make changing power very awkward.