Sorry, I did order and try the unit from ZP, it pales in comparison to most every zapper that I have tried and that is quite a few. This includes several units that we do not make. Maybe the one I got is just weak or something. Frequency is about 15 kHz.
As for the difference in frequency, I will try to post some actual data in the next few weeks if I have time. There is a definite difference according to our customers who try both.