Complex sentence: There are no data about his place or date of birth, but he is assumed to be a native of Zwickau itself; and his activities both in and away from Zwickau are not well-documented.
Split into simpler sentences: There are no data about his place or date of birth, but he is assumed to be a native of Zwickau itself. His activities both in and away from Zwickau are not well-documented.