[ldolse]

You would only see css styles like that if he did an ePub to ePub conversion - one of the major reasons Tweak ePub was created was to avoid having Calibre manipulate the css the way it does in a full conversion.

If his edits were actually edits to the content and not formatting, and you need to find and merge them into your original ePub the simplest method I've found is to convert both versions to txt - I usually enable smarten punctuation under look and feel to attempt to normalize the txt across both versions. Then compare the two versions in a diff tool - I've found P4merge (free download) seems to work best with book length docs.