Complex sentence: Contemporary history ("Liber pontificalis") dwells chiefly on Zachary's great personal influence with Liutprand, and with his successor Ratchis; his tact in dealing with these princes in a variety of emergencies contributed to save the exarchate of Ravenna from the Lombard attacks.
Split into simpler sentences: Contemporary history ("Liber pontificalis") dwells chiefly on Zachary's great personal influence with Liutprand, and with his successor Ratchis. His tact in dealing with these princes in a variety of emergencies contributed to save the exarchate of Ravenna from the Lombard attacks.