Not sure if this is the best place to ask but is anyone aware if any of the major books about or written by Heinrich Dathe or Bernard Blaszkiewitz are available in English?
I very much doubt that there are any books written by Dathe which are available in English, but I suppose it is possible that Blaszkiewitz might have translated at least *some* of his books given the fact that he was involved in the translation of those English-language guidebooks published during his tenure at Zoo Berlin. If so, I certainly haven't come across any such material myself.
As for books about Heinrich Dathe in English-language, probably the closest you can get would be the excellent The Zookeeper's War - a translation of Der Zoo der Anderen, the book by Jan Mohnhaupt which was recommended upthread by @lintworm , and which covers the history of both Berlin collections from the height of WWII to the end of the Cold War, along with biographical material relating to both Heinrich Dathe and Heinz-Georg Klös.