Complex sentence: Another coup was attempted in 1121 to install Tianzuo's son, the prince of Jin, onto the throne, but was again thwarted and the prince executed, and most of the coup organizers defected to the Jurchens' camp.
Split into simpler sentences: Another coup was attempted in 1121 to install Tianzuo's son, the prince of Jin, onto the throne, but was again thwarted. The prince was executed, and most of the coup organizers defected to the Jurchens' camp.