I'm a bit amazed he's using zoom lenses. That has to be tricky to synchronize precisely, at anything but the end settings. Though it seems he has made a jury-rigged band which turns them both at once, ingenious if it works well.
Not as "jury-rigged" as it appears, methinks. The link between the lenses appears to be using Posi-drive (tm) elements which, along with the machined bracket coupling the two bodies, imply careful design, precision machining, etc. Might yield surprisingly accurate results, who knows...
The twin-core variety he's using is composed of two highly flexible stranded steel cables encased in polyurethane (PU), with PU "ladder rungs" molded at regular intervals. The corresponding pulley has a smooth race on either side for the cables and a string of teeth in the center meshing with the "ladder".
The end result is something indeed very similar in principle to a chain drive, except that the resulting motion doesn't have the velocity wobble associated with rigid-link chain drives (humm, I don't know how I could easily explain this one... sorry).
Bottom line: excellent load capability and outstanding performance, stability and wear resistance, and also self-lubricating in a lightweight assembly. Probably wouldn't be tough enough for a bicycle (would be pointless anyway, don't need the precision there), but is pretty good in small precision assemblies. Downside is that you have to get the belts made to size, you cannot adjust the length as you can do with a chain (by adding/removing links). I myself would consider it more like a very rugged timing belt (which I probably would have used in his setup, the choice of posi-drive is a bit odd to me).
Thanks, friend. Hmmm, quite interesting. The comments do show that this guy, David Klutho, is a pro who has written books about 3D photography and so on.