Conversation so far:
When did the Spanish colonization of Mexico begin?
The Spanish conquest of Mexico is generally understood to be the Spanish conquest of the Aztec Empire of 1519–21.
What happened during the Spanish colonization of Mexico?
The Spanish conquest of the Aztec empire.
What was so spectacular about the Spanish conquest of the Aztecs in 1519?
The fall of the Aztec Empire was the key event in the formation of the Spanish Empire overseas, with New Spain, which later became Mexico.
What else happened during Spain's initial conquests in Mexico besides the formation of the Aztec empire?
The victory over the Aztecs was relatively quick, from 1519 to 1521, and aided by his Tlaxcala and other allies from indigenous city-states or altepetl.
Were the indigenous city-states which helped Spain conquer the Aztecs eventually conquered themselves?
These polities allied against the Aztec empire, to which they paid tribute following conquest or threat of conquest, leaving the city-states' political hierarchy and social structure in place.
What else happened around the time of the Aztec conquest by Spain besides the Aztec Conquest?
The conquest of the Aztecs matched in scope by the victory over the Inca empire in 1532.
What else is interesting about the Aztec Conquest besides occuring around the same time as the Inca conquest?
The Spanish conquest of Yucatán was a much longer campaign, from 1551 to 1697

Question: Why was is longer to conquer the Yucatan?
Self-contained rewrite: Why was it longer for the Spanish to conquer the Yucatan compared to the Aztecs?