I've looked into this image extensively, and talked with lots of other folks who did so, too. The zig-zag is the shaking camera on the tripod as the time exposure is activated prior to settling into position.

What misleads observers is this: the white streak across the sky is the persistent ion trail left behind a passing shuttle entry, NOT the motion of the point-source fireball across the time-exposed field of view. So once the camera settled into position with the shuttle ALREADY midway through the field of view, the already-existing white persistent trail of its earlier passage ALSO registered on the optical imaging memory.

You really have to see this effect yourself to appreciate how startling (and unexpected) it is. So getting fooled by misinterpreting the source of the visual pieces of the image is excusable. What's not excusable is for conspiracy nuts to shut their minds to real physics and careful investigative techniques, in order to propagandize an idiotic pet theory.