Complex sentence: Naram-Sin (2155 BC--2119 BC short chronology) was the third successor and grandson of Sargon of Akkad; under Naram-Sin the Akkadian Empire reached its zenith.
Split into simpler sentences: Naram-Sin (2155 BC--2119 BC short chronology). Under Naram-Sin (the third successor and grandson of Sargon), the Akkadian Empire reached its zenith.