Or it could be guttulata (considered by some to be a location variant of zonatus).
If you check the book American Cichlids II Large, by Staeck and Linke, page 21, your fish is almost identical.
While zonatus supposedly comes from rivers flowing to the the Pacific coast in the state of Oaxaca, its sister species guttulata, is from Lake Amatitlan in Guatemala, and more inland in the Mexican state of Chiapas.