The book, "Family Records or genealogies of the first settlers of Passaic Valley and Vicinity", lists the Zachariah that married Rosannah (nee BOWMAN) as the son of Zachariah (b. circa 1742) and Mary LITTELL (b. 1749).The book also states that, "Zachariah Van Sickle, with his family, excepting Huldah, removed to Western Pennsylvania."This refers to Zachariah Sr., born c. 1742.This info. definitely fits with the Zachariah from Greene Co. PA.
P.S.The Passaic Valley book does not list that the Zachariah that married Rosannah BOWMAN had a sibling named Samuel.His father was named Samuel though.Could the Samuel VAN SICKLE in your records be old enough to be Zachariah's father??