Hernandez's goal in the 53rd minute marked the second straight match in which he has scored for Mexico, after he produced two goals in a 5-0 victory over Bolivia in San Francisco last week. The 21-year-old, who is the leading goal-scorer in Mexico's fist division with eight goals in seven games for Chivas Guadalajara, opened the scoring as he headed a cross from Carlos Salcido past New Zealand goalkeeper Glen Moss.
Vela, who plays for English Premiership club Arsenal, replaced Aldo De Nigris to start the second half. He doubled the score in the 57th minute, as he eluded three defenders and slotted the ball past Moss. Vela muscled his way past defender Ben Sigmund on the edge of the penalty area, then out-manoeuvred two other New Zealand players to score.
The two-goal lead warmed up the largely pro-Mexico crowd of 90,526 crowd on a damp, chilly night at Pasadena's Rose Bowl stadium. New Zealand's best opportunity had come in the fifth minute when Boyens, of the New York Red Bulls, headed a corner wide.
For Mexico the match was the second in a series of six friendlies in the United States as they prepare to open their FIFA World Cup campaign against hosts South Africa on 11 June. Their first-round group also includes France and Uruguay.
The friendly offered Mexico coach Javier Aguirre a chance to see some of his Europe-based talent, including Vela, Salcido, Rafael Marquez, Andres Guardado and Giovani and Jonathan Dos Santos.
New Zealand, who will be playing in just their second FIFA World Cup, had to make do without defenders Ryan Nelsen and Ivan Vicelich. Nelsen, the team captain, suffered a hyperextended knee in Blackburn Rovers' 3-0 English premiership win over Bolton Wanderers in February, while Vicelich is suspended.
New Zealand will travel to Europe in late May for further warm-ups against Serbia and Slovenia. In the first round of the FIFA World Cup they are drawn in Group F with defending champions Italy, Slovakia and Paraguay.