If you want to use different viewing angles you can change the lenses on the Nex5 (e.g. 24mm, 50mm) and do this with a Zenmuse, but you have to rebalance after each new lens, your you have to balance for the most heavy lens and balance for the others with trim weights on the lenses. If you really want to zoom in flight you have to go for a camcorder ( e.g. Sony CX 730 is a popular one) and a good BL-Gimbal for that.
Here Zenmuse with Sony Nex5 and Kit 18-55mm at 18mm:
Here Zenmuse with Sony Nex5 and SEL50f18
Here Sony CX250 and Zoom on BL-Gimbal:
best regards
Ferdinand
P.S.: I strongly doubt, that you can mount and fly a Zenmuse for Nex5 on an xaricraft 650.