Southern started slowly but played superb rugby in the remaining 60 minutes to beat Zingari-Richmond in cold conditions at Montecillo.
Southern dominated possession and territory during that time and the accurate goal kicking of Ben Patston helped the Magpies lead 16-0 at the break.
The strong Zingari defence shut down Southern's attacking moves in the first spell. But the pressure steadily mounted and was exploited by Southern in the last 40 minutes when it added three tries and 24 points.
Patston kicked his fourth penalty after 10 minutes, and when winger Hamish Buick scored after a 40m move down the blindside the lead was 26-0.
Halfback Robbie Smith was the director of the troops and his skills stood out in the second spell when Southern dominated the game.
The game was won in the forwards, with No 8 Tom Franklin and lock Sam Gibson controlling the lineout.
Franklin was particularly good at setting up phase ball from which he and midfield back Luke Herden scored tries in a three-minute period midway through the second spell.
Centre Apelu Alapati was dangerous with the ball and was able to slice through the defence.
The best players for Zingari were second five-eighth Ben Kent, halfback Fumiaki Tanaka and flanker Chris Bell.
Southern 40 (Hamish Buick, Apelu Alapati, Luke Herden, Tom Franklin tries; Ben Patston 2 con, 4 pen; Bryce Hosie 2 con), Zingari-Richmond 10 (Chris Bell, Ben Kent tries). Halftime: Southern 16-0.
