The USB 1.1 on the Zaurus won't work with most printers (only newer spec-ed have a peer-to-peer capability).
IrLpt should be possible, but you need the print function to be built in to the application (note that most QPE demos have a print option, but I don't think QPE does).
There are two other problems. First, you need to talk a printer protocol, and most printers have their own, although PCL and PostScript are the most common. Even then, color v.s. monochrome can be a problem. So even a "print screen" type function becomes difficult.
If you already have a printer that can accept CF or SD flash cards, you should already be able to print pictures already there by using the cards. A program to screen-capture to JPEG would be easy (there is already one to BMP with shift-function-C?).