Zingari-Richmond was beaten but not disgraced when it lost to Harbour 27-8 in bitterly cold conditions at Montecillo.
The scores was 8-8 at the break and Harbour only led 15-8 after 32 minutes in the second spell, but two late tries gave Harbour the bonus point and a comfortable winning margin.
It was a committed Zingari team that put up a tenacious defence and shut down the fleet-footed Harbour backline.
None did this better than second five-eighth Ben Kent with his strong tackling. It was the rush defence by Zingari that forced Harbour to adopt different tactics in the second spell.
Harbour has probably the best front row in the competition and it was able to exert pressure at the scrum.
Pieter van der Merwe, Pete Mirrielees and Ben Nolan are all powerful on the drive and the rolling maul.
Harbour's three second-half tries all came from powerful driving play by the pack.
The first after two minutes came after a prolonged drive into the Zingari 22m before halfback Johnny Legge darted 15m down the blindside for the try.
The pack went the whole way for the second try after 32 minutes when van der Merwe used his strength to crash over the line.
The forwards drove for several phases on the call of fulltime for the bonus-point try scored by flying fullback Ollie Cuthill when the ball was released to the backs.
Cuthill added pace when entering the line and was the best of the Harbour backs. Legg was dangerous with his sniping runs.
The other forwards to impress in the Harbour pack were flanker Angus Duckett, with his work at the breakdown and his ability to make ground with the ball in hand, and lock Sam Ready.
Ready made 11 clean takes in the lineout.
Lock Brady Carmichael, who made eight clean takes in the lineout, No 8 Chris Bell and prop Jeremy Bekhuis were the best of the Zingari forwards.
Harbour 27 (Ollie Cuthill, Corey Kara, Johnny Legge, Pieter van der Merwe tries; Lance Taylor 2 con, pen), Zingari-Richmond 8 (Nathan Napier try; Mark Hunter pen). Halftime: 8-8. Referee: Jeff Grubb.