Hello Helmut,
I am related to the Ziegler side of the Isaak family. Christine Ziegler (b. 12 Mar 1834) in Beresina was the daughter of Adam Ziegler and Katharina Tramnitzke. Katharina was my great-grandfather's aunt. Do you have any more information on Adam & Katharina's children from Dennewitz?
If there are any of Christine and August's children (or grandchildren) on line, please contact me. I would love to meet my distant cousins.