The lowland books

Maya

Older writing, older zero, the same 260-day count under another tongue. The Mexica adopted and learned. They did not invent the sky-science they used.

What the Mexica took from the Maya

The 260-day count: Maya tzolkʼin, Mexica tonalpohualli. Twenty signs, thirteen numbers. Same engine.
The 365-day vague year (haabʼ / xiuhpohualli) running beside it.
Vigesimal place value. Maya wrote zero as a shell. Mexica counted 20s with flags on tribute lists.
Feathered serpent: Kukulkán / Qʼuqʼumatz → Quetzalcoatl.
Ballgame, maize, the idea of successive worlds, the quetzal as the bird of preciousness.

Classic Maya cities were already in ruins or changed when the Mexica rose. Knowledge moved through Teotihuacan, the Gulf, and the Postclassic Maya of Yucatán (Chichén, Mayapán). Adoption is documented in the shared calendar, not in a fairy tale of one people turning into another.

Hunab Ku as later Yucatec teaching drew it. Classic Maya did not write this glyph this way. We keep it as a teaching mark, and we say so.

Hunab Ku in stone — The spiral-and-ray. Sister of Ollin.

Kukulkán and the quetzal echo

El Castillo at Chichén Itzá is a stone calendar: 91 steps on four sides plus the top = 365. At the equinox the shadow of the rattlesnake descends the north balustrade. A clap at the stair returns as a quetzal chirp — the steps scatter the sound. Kukulkán is the Maya feathered serpent the Mexica knew as Quetzalcoatl.

Gods that map across

Itzamna / Hunab Ku

Sky and making. Hunab Ku (“one god”) is mostly colonial Yucatec. Itzamna is the older name in the inscriptions.

Kukulkán

Feathered serpent. Quetzalcoatl in Nahuatl.

Chaac

Rain. Tlaloc in the highlands.

Ixchel

Moon, medicine, weaving. A Maya goddess. The Mexica moon at the foot of the temple is Coyolxauhqui — a sister story, not the same name.

Day signs, two tongues

Cipactli is Imix. Ehecatl is Ikʼ. Ollin is Kaban. Xochitl is Ajaw. The tonal page keeps all twenty with both names. The count is one.