Even though markitdown is a Microsoft project, it's just a thin wrapper around a bunch of 3rd party Python packages. For example, to go from docx to Markdown, it uses mammoth to convert docx to HTML[0], then uses markdownify to convert the HTML into Markdown[1].

[0]https://github.com/microsoft/markitdown/blob/da7bcea527ed04c... [1]https://github.com/microsoft/markitdown/blob/da7bcea527ed04c...