Complex sentence: The imperial and US customary systems of measurement are two closely inter-related systems of measurement derived from the English system of measurement units which itself can be traced back to the Ancient Roman units of measurement, and Carolingian and Saxon units of measure.
Split into simpler sentences: The imperial and US customary systems of measurement are two closely inter-related systems of measurement. They are both derived from the English system of measurement units which can be traced back to Ancient Roman units of measurement, and Carolingian and Saxon units of measure.