The Cowgirls and the Bearkats had battled to a scoreless tie after 90 minutes of action. Sam Houston totaled 12 shots during regulation while the McNeese took 10 shots.
Michelle McCullough made six saves as she picked up the shutout in goal for the Bearkats, her first of the season.
Five minutes into the overtime, Zak fired a shot saved by McNeese goalkeeper Cassandra Reed. After a punt by Reed, Zak won the ball near midfield, rushed past a defender and scored the match-winner. Zak led the Bearkat offense with four shots.
The victory upped Sam Houston's season record to 6-9-1. The Bearkats stand 2-2 in Southland Conference play. McNeese State dropped to 7-8 for the year and 2-3 in league action.
Sam Houston faces three matches at home this week to wrap up the Bearkats' 2011 schedule of contests at Joseph Pritchett Field.
The Kats play host the Central Arkansas Wednesday at 7 p.m., Nicholls Friday at 7 p.m. and Southeastern Louisiana Sunday at 1 p.m.