I am looking for unbiased test results or reviews of "cold
galvanizing" paints (ZRC, for example).  I want to see their ability
to protect steel from rust compared to other methods including hot dip
galvanizing and conventional enamel spray paints.  Ideally, the
testing process would include scratches or cuts through the coating
down to bare steel.

Comparison to powder coating would be a bonus, but is not required. 
Comparison of the effectiveness of different brands of cold
galvanizing paints would also be highly desirable, but not required in
the answer.

There are some good reports at http://www.zrcworldwide.com/tr-toc.htm.
This is a company that makes zinc compounds, but they are scientific
reports, and good info about what you are seeking.