Complex sentence: Omri (Ahab's father and founder of the short lived Omri Dynasty) seems to have been a successful military leader being reported within the text of the Moabite Mesha Stele to have "oppressed Moab for many days".
Split into simpler sentences: Omri (Ahab's father and founder of the short lived Omri Dynasty) seems to have been a successful military leader. He was reported within the text of the Moabite Mesha Stele to have "oppressed Moab for many days".