CP units that fought in most of the major Eastern campaigns?

[DixieDivision1418]

Does anyone know of any German/Austro-Hungarian units that fought in most of the major campaigns in the East? My reason for asking is that I've been considering writing a book from the perspectives of a German soldier and an Austro-Hungarian (probably a Croatian) soldier fighting on the Eastern front, and I had hoped to include most of the major battles of the Eastern front.