html to mp4 conversion can be interpreted many ways, from using MP4 video on HTML web page to text-to-speech exports from HTML source to MP4 audio as output format.
The first thing is certainly doable with many HTML/web page editors and you can find plenty of tutorials and guides for this on the Internet. As for the text-to-speech conversion, you have to use dedicated software for that, for example Balabolka.
Updated: February 6, 2023