Two different things you can save
My List saves a reference to a film or series. A video download stores playable media in an app that supports offline viewing. Adding a heart in Zmov does not create a movie file or make an episode available without a connection.
Prepare inside the viewing app
Open the title with your chosen service and check whether its app offers a download. The option can depend on the title, region, device and plan. Choose the audio and subtitle tracks you need, and test the downloaded item before leaving reliable internet access.
Plan for space and expiry
A larger download quality can use more storage, while a small screen may not benefit much from the largest available file. Check the app's expiry information and leave enough battery for the journey. Some apps need an occasional connection to keep downloads usable.
Bring your progress back
After watching offline, update your Zmov episode checkpoint yourself. Another service's app does not report that progress to this browser. A list backup is useful for carrying your choices to a replacement device, but it does not transfer downloaded videos or account access.