GitHub Pages
The issue
Since Zim is building static website, you can host the generated content on GitHub pages.
If you are using a template which provides resources, all the resources will be copied to a _resources folder in the static website. And since GitHub pages is using Jekyll, all the files and folder names starting with an underscore are ignored during the generation process… That's why, your _resource directory will be ignored in GitHub pages.
The "solution"… which does not work actually!
Since the issue is well known, GitHub provides a walkaround. You can turn off Jeckyll by adding a .nojekyll file in the root path of the repository. It solves our issue… but now, you can't use the compression anymore !
That's why all modern browsers will not be able to access some ressources… whereas curl can.
This souds incredible, but depending if you are using the --compress flag with curl, you obtain a 200 or 404 error code.
The solution
Fortunately, GitHub provides another walkaround. We can tell Jeckyll to parse _resources folder as any other standard folder. To do this, just add an _config.yml file in the root path of the repository with the following content : include: _resources
And now, everything works as expected!