Zenphoto manages some types of multimedia files (image, video, music, ...) hosted on its own webspace, but is not natively designed to manage online videos (eg videos hosted on YouTube).
But in fact, there is a way since Zenphoto 1.2.6 to add online videos in the gallery (see here for all details):
- In admin panel, activate the class-textobject plugin
- In an album in your gallery, download a text file (.txt, .htm or .html) containing embedded code to your video
- Optionally use a different thumbnail than the default one by following these instructions