Using a timestamp within your static resource path seems a bit problematic if that resource is constantly updated (like a stylesheet).
Following the official doc and looking at the generated meta tags in a page, I found that the following path works in my community app:
ZIP Inside ZIP
If you have a ZIP inside the ZIP, this will fail. You can't access the resources inside of that file, as the system won't repeatedly/recursively decompress files this way.
You can verify this by downloading the static resource itself in your browser: