It's built on remark.js, supports images, [[wikilinks]], and raw html in markdown, as well as custom layout.html customizations. Once the site is built, you can open the output `.html` pages without a server to preview.
Demo: here is a post expanding on the "whys" on my personal site (built with ZenMD) - https://idealistspace.com/zenmd
Just made the Github repo: https://github.com/randomor/zenmd public if you'd like to look at the code.