[rkomar]

I suspect that you can create the file in the system/config directory, and it will be used. You only need to add entries for the archive files you want to read with pbimageviewer (see the first post for more info). Other file types will be handled by the system's default extensions.cfg file that is hidden in another partition.

If you are desperate, you can unpack the archive file into a directory with separate image files, and then run pbimageviewer from the Applications tab. When run that way, the program pops up a directory chooser, and you select the directory that contains the separate images. The PocketBook API doesn't offer a file chooser, so there is no way to select an archive file that way (they expect that you will use the Library tab for that).