>- what I heard is that you cannot zap anything in a "hollow organ".
I heard that a long time ago but find that it is outdated because they did not have augmentation footpads at the time that statement was made. Also, at this point in time, almost all zappers were 30 kHz and since then, lower frequency zappers have been noted to penetrate better.
Sadly, despite efforts to this extent, there has not been anyone found to be willing to do a good scientific study on this or other aspects of zapping.