The Eaglets extended the lead in the 56th minute as captain Muhammed unleashed a stunning which was too hot for Mexico goalkeeper Raul Gudino. The goalkeeper spilled a rebound for directly to the feet of Iheanacho, who made no mistake dispatching his sixth goal of the tournament.
Muhammed added a third with ten minutes left, curling a sublime free-kick into the top corner.
Coach Garba has now won the tournament as an assistant coach in 2007 and head coach in 2013.