Well, although I would have preferred that Ambrosia get SnapZPro working as before without resorting to the kludge of other software on top of it, I decided to try some of the options discussed above. Couldn't get any results from Sound Siphon, so reluctantly (in view of the mixed results reported), I tried Soundflower. [Note that as of today, the latest version of the disk image file is 1.6.6b. Many earlier versions are floating around!]
Using the Soundflower and Soundflowerbed settings nicely illustrated by flgrimes in the above post, I was able to reproduce what SnapZPro used to do for me -- record video (and also subsections of the video window) with sound included.
flgrimes, thank you very much for the detailed information you provided.
iMac (Retina 5K, 27-inch, Late 2014)
OSX Yosemite 10.10.1