Original: This episode in the conquest and colonization of the Americas began in the early 16th century, but was a more difficult and lengthier exercise in subjugation than the equivalent campaigns against the Aztec and Inca Empires.
Simplified: This part of the conquest and colonization of the Americas began in the early 16th century, but it took more time than the similar campaigns against the Aztec and Inca Empires.