The top-seeded Golden Knights, who improved to 8-0 with the win, scored at will in building a 28-0 halftime lead.
Connor Breit ran for a pair of TDs, and Rob Klebetz and Brian McGreevy each returned punts for scores.
Nanuet is scheduled to host No. 5 Putnam Valley Saturday in the semfinals.
Irvington fell to 3-5.
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