Complex sentence: Eventually, the Spanish prevailed in the struggle over the central valley and went on to defeat the chief Petecuy, whose tribe inhabited the area between the river Lilí and the Western Cordillera.
Split into simpler sentences: Eventually, the Spanish prevailed in the struggle over the central valley. Before taking control over the region, the Spaniards had to defeat the chief Petecuy, whose tribe inhabited the area between the river Lilí and the Western Cordillera.