Instead of cutting up the pages into little pieces, how about you just scroll, pan and zoom, like it's been done since the good old PDA days? Doing it automatically may fragment a few dialogue bubbles along the way, forcing you to go back and forth between images. Not a very good experience, unless it's an old comic or something like
Watchmen, where all the scenes have a fixed or semi-fixed size on the page (
link).
By the way, CBR/CBZ are just RAR and ZIP archives. That's what the "R" and "Z" stand for. And if your e-reader doesn't support them, it most certainly supports JPG, PNG, etc. Just extract the images and copy them to your e-reader.