Oops, I found a bug. The installation script incorrectly associated the djvu file format with zipbrowser if you had installed the preview of the djvu plugin for the new firmware (
https://www.mobileread.com/forums/sho...t=73790&page=2 ) before you installed zipbrowser. If you experience this problem, just reinstall the djvu plugin.
Here's an updated zipbrowser that fixes this.