In Theory Zenpoint
can work with MP4 files so you should be able to configure it.
A good forum post about this is https://download.zenpoint.org/Forum/View/1747/Music_Videos
The important part of this is that if you need to configure the filter as *.MP4 (full stop after the * is important).
When I first started I tried using MP4 files and found that the codecs can be a bit hit and miss.
You can try to load the codec's from Shark007 https://shark007.net/ and hopefully that will resolve the issues.
Zenpoint still uses the old windows Media Player under the covers and MP4 support in this can be troublesome.
I now routinely convert the files to MKV using Handbreak https://handbrake.fr/
It would be good if the Developer could post what attributes a media file needs to play as I have also found you sometimes need to convert audio/video to different configurations otherwise it wont work.