Complex sentence: He tried to re-establish the Nguyen lords' authority but unsuceeded; and then was captured and executed with his followers and almost all family members by Tay Son rebel general Nguyen Hue in 1777.
Split into simpler sentences: He tried to re-establish the Nguyen lords' authority but unsuceeded. At least, he was captured and executed along with his followers and almost all family members by Tay Son rebel general Nguyen Hue in 1777.