The README fails to address the elephant in the room, which is that usually shell scripts mainly call external commands; as far as I can tell there is no documentation of which built-ins are supported?
That said, in a similar vein, you could probably create a bundler that takes a shell script and bundles it with busybox to create a static program.
Disclamer: the elephant in the room has nothing to do with ElePHPant, the PHP mascot.
I submitted this because of the new "Live Folders" feature. For a long time, RSS has felt relegated to third-party extensions or separate reader apps. Zen's update integrates RSS feeds and GitHub Issues/PRs directly into the sidebar tab hierarchy.