It seems that the [GitHub repo](https://github.com/rooney/zencoding) for Zen Coding in emacs is not actively maintained (last commit was a year ago), and there are some features missing, e.g. the `html:5` "tag".

I couldn't find any other sources for the emacs mode. Does anyone know if there exists an updated version?

The Zen Coding google group links to EmacsWiki which in turn links to the above mentioned GitHub repo.