From: http://www.celerina.com/zapotecs.html
Ancient Zapotec ritual activities provide clues to their pre-Hispanic
religious beliefs. Mortuary rituals were particularly important
in pre-Hispanic Oaxaca. The ceramic urns that were used as funerary
offerings during these rituals provide insights into pre-Hispanic
Zapotec beliefs.
A common class of urn represented Cocijo, the Rain God (cocijo means
lightning in Zapotec). Others are said to have represented the God
with Helmet of a Wide-Billed Bird, God with a Serpent Mask, and
so forth.
It is believed that Zapotec urns represented powers or gods just
as the images of saints in a church do. Some urns represented leaders
or priests who had taken on special powers. By wearing a mask, the
person represented on the urn was taking on extrahuman forces. The
Zapotecs may have venerated and respected certain spirits and forces,
communicating with them by means of an image of a man accompanied
by the appropriate symbols. Particular symbols may have represented
certain powers, deities, or gods and may have been invoked during
specific events or ceremonies, which may explain why some images
and sets of symbols appear frequently.
Little is known about the beliefs surrounding these deities, but
their constant presence in the archaeological record implies that
they were of great importance in Zapotec life. Often they are represented
as abstract symbols: just an eye, beak or snout. But it appears
the wearer of the symbol was imbued with its power.
The Zapotecs assimilated the religion of the Spanish missionaries
during the 16th century. Today, they are predominately catholic.