For what it's worth, I'm having the same problem on my Kindle 2: alt-shift-zero doesn't seem to do anything on the Kindle 2, at least not on mine. I sent Amazon a support request about it a day and a half ago, no answer yet.
I'm also having trouble getting images onto it, period. Copying them over, fine. Alt-Z to compile them into a "book" on the home page, fine. Open the book -- not so fine. Most of the time, it looks like nothing happens, the screen never redraws with the image. Although I have figured out that if I hit "f" for full-screen twice, the redraw works. But then I have to hit "f" twice for each page, to show it. I tried it with GIFs and JPGs, both of them exported from Irfanview, same result. I got an even worse result with BMPs exported from Irfanview, the Kindle insisted there were no recognizable image files in the directory.
Any advice? Amazon is taking forever to answer my questions.