Manchester United striker Javier Hernandez followed up his opening day hat-trick against El Salvador with two more goals, in the 36th and 76th minutes.
Giovani Dos Santos weighed in with two of his own in the space of five second-half minutes and substitute Aldo de Negris also found the net.
"We knew that game was gong to be complicated," said Mexico coach Jose Manuel De La Torre. "They were going to clog our spaces and counter-attack. But we needed to take care of the important opportunities.
"You could see in the first half we weren't effective. In the second half we took advantage of opportunities and you see the result."
The early Group A match saw Randall Brenes score an equaliser deep into injury time to rescue a draw for Costa Rica against El Salvador.