Complex sentence: Zabel co-authored with Richard Dolan the book A.D. (After Disclosure) 2012, which concerns the subject of an extraterrestrial presence on Earth covertly interacting with humans and governments and what develops when this fact is made public.
Split into simpler sentences: Zabel co-authored with Richard Dolan the book A. D, (After Disclosure), 2012. On the subject of Full Disclosure of an Extraterrestrial presence on Earth interacting with Humans and governments covertly and what scenarios may develop when this fact is made public.