How do I remove bitterness from zucchini?
Mild bitterness in zucchini, like that found in cucumber, may be
  result from environmental factors such as high temperature, low
  moisture, low soil nutrients, etc. The bitterness is caused by
  compounds called cucurbitacins. There is also a rare condition which
  can cause extreme bitterness in zucchini. A compound called
  Cucurbitacin E is found in wild species of squash, but is extremely
  rare in cultivated species. (Univ. of Arizona)


Having bounced around to the various other sites I basically had what I've heard anecdotally before confirmed; salt and lay out to drain liquid. I suppose the implication is that by dessicating the zuke a little bit, it can remove the Cucurbitacin (which is a steroid developed to ward off herbivores). Putting the zukes in salt water is also recommended by some.

It appears that people can become ill from incredibly bitter zukes, so be wary of eating extremely bitter ones. In this case, you may want to follow the wisdom of your taste buds and drop the zucchini in the trash.