Extracting resources from Heroes 3.

I didn't even think you could get so involved with this...)

Here you'll find everything you need. DefPreview in particular.
https://grayface.github.io/wog/#Def-Preview

And with DefTool, you can further experiment.
https://grayface.github.io/wog/#Def-Tool

Regarding "extracting resources..." - there's MMArchive. And, judging by the video, you know how to use it. What's the problem?