'Conquest of Mexico'

[La Fayette]

Attention please: THIS IS A SPOILER THREAD
Don't read it if you wish to play that scenario without tips.

IMO victory in this scenario is mostly based upon using the right unit for the right purpose:

1) Early game:
Tenochtitlan is the one and only Aztec city, surrounded by foreign cities and mountains. All those cities have walls: attacking them with the units you have would be committing suicide.
What must be done is scouting, in order to find a less crowded area and try to grow there. The right unit is called Arrow Knight (an improved Aztec Explorer, 'All as roads', 'See 2 squares', Defense = 2).
I used 5 of those in my game during the first 10 turns, before sending the first settler to the less crowded-best fitted area.

2) Early Mid game:
Once you have built what you think is the right minimum number of cities to start waging war, you need an unit able to attack walls with nice odds (you may start sooner than if you guessed you were going to fight a strong civ, since most of the surrounding cities (named Chichimec) are coloured red and seem to behave like 'peaceful Barbs' ).
The right unit is the Slinger (attack = 7, with FP = 2), but the Pipiltin (attack = 6, HP = 2) is even better, provided you manage to research quickly (the tech tree towards Slingers is shorter than the one leading to Pipiltin).

3) Late Mid Game:
As soon as you feel strong enough to start trading instead of just building Slingers and Pipiltins (I would advise to start soon, since it provides both gold and beakers, as anyone knows), the right unit is named Pochteca (a cheaper Aztec caravan = 30 shields).
In my game, I chose Tlaxcala as target city (far bigger than the other cities nearby) and sent all my Pochtecas there during about 100 turns.
Of course more scouting and more fighting is required in the meantime, especially because when you attack a foreign settler, you get an Aztec slave who is almost equivalent to an engineer.

4) Late game:
The Readme File warns you from the start: no hope to fight the mighty Conquistadores with your weak Aztec units. Clearly you need diplomats and lots of gold.
The right unit is named High Priest (attention = only one move !; it is therefore advisable to build some kind of 'Atlantic Wall' to slow down the mighty Spaniards and be able to bribe them before they kill too many Aztecs).
In my game, I chose to have forest or jungle all along the coast, with a road behind, and hundreds of High Priests wandering along that road (with a Treasury of 29900 gold, just below the cap).

5) End game:
1546 is the end of the scenario.
Personally I got bored around 1530 (all Conquistadores previously bribed or killed by bribed Conquistadores) and started playing spacebar (the result being that I left about half a dozen Chichimec cities on the map, that I could easily have bribed, had I sent some of my numerous canoes over there, with High Priests onboard).
The other problem is the victory condition: the Readme File mentions 33 objective cities, but I never saw more than 12, which gave me a Marginal Defeat (though almost the whole map was Aztec).

[Mercator]

I did focus on conquering the surrounding cities first, so I guess that was my undoing... It slowed down my early expansion, and thus research.

I never was much of a trader either , so I didn't have nearly enough money to bribe any Spaniards.

Instead, I tried to build as many (cheap) units as possible, and fill up forts along the coast. Not to kill any Spanish units, but just to slow them down enough to keep them away from my objective cities. It worked for a while, but not long enough.