[rejap]

it is a zip with collection of xml files. Diff on as-is xml from word doesn't work, there are a lot of false positives. Things looks the same from a user perspective, but internally it is different. You would have to interpret/render the content to really tell if it is different. There is also plain tracking noise of word itself.

However, diff on word xml is perfect tool to understand how the microsoft interprets the spec.