University scored eight tries to beat Green Island 48-9 in a performance which singles the students out as the other major threat in the competition.
Harbour rebounded from its first-round loss against Southern to beat Taieri 28-5, and Dunedin edged Alhambra Union 24-22 after trailing 17-5 at the break.
Southern: 37
Zingari-Richmond: 19
Southern's big pack roared into action to set up a 37-19 win against a spirited Zingari-Richmond at Bathgate Park last night.
The Magpies dominated at scrum time with their front row of Mike Mata'afa, Cameron Keech and Hisa Sasagi getting the home team on the front foot.
Powerful No8 Mika Mafi had a dream ride at the base of the scrum and made some telling runs. Fellow loose forward Josh Clark had another typically busy game and he was on hand to score the opening try.
When Zingari fluffed a grubber kick, Clark scooped it up and ran in from about 20m to score.
The visiting team replied with a wonderful try. Lock Tom Rowe cleared some defenders with a big skip pass. Flanker Jack Wolfreys got his hands on the ball and charged down the left wing and offloaded to impressive centre Taylor Fiddes, who ran around and dotted down under the posts.
Southern was soon back on top when Sasagi barged over and, moments later, Kyle Harris got across the line following a midfield break.
Zingari trailed 25-12 at the break and fell further behind when Josh Walden took a quick tap close to the line. The ball was swung out to the right and replacement fullback Josh Buchan provided the finish.
Zingari kept battling and was eventually rewarded when halfback Ronin Ainsley dived over from the base of the ruck.
However, Southern had the final say with big prop Mata'afa bulldozing his way over from the back of the lineout.
Dunedin: 24
Alhambra-Union: 22
Dunedin needed two penalty tries in the final quarter of the match to overcome Alhambra-Union 24-22 in a thriller at Kettle Park.
The home side took a good 60 minutes before it was able to get itself into the game through its powerful pack. By then Alhambra had built a 22-10 lead.
The visiting side scored in the first few minutes after second five-eighth Ben Quaqua busted through in the midfield and got the ball to lock Hayden Fluery to score.
Winger Zac Harrison-Jones replied for Dunedin but Alhambra dominated the next 20 minutes.
Fullback Jona Nareki broke the defence and winger John Tapululuheu finished off. Then right on halftime Dunedin turned the ball over and Nareki sprinted off to score.
Dunedin had kicked too much ball away and could not win any lineout ball. The game looked over with 15 minutes to play.
Alhambra led by 12 points but Dunedin started to win some lineout ball and got back into the match with some tight forward play.
The Sharks had two or three scrums close to the line before the referee lost patience with all the collapses and awarded Dunedin a penalty try.
With a few minutes remaining, Dunedin was on attack again and driving towards the line following a lineout. Prop Donald Brighouse was caught in a head-high tackle as he was going over the line and dropped the ball. Dunedin was awarded a penalty try and held on to win.
Harbour: 28
Taieri: 5
For the most part, Taieri was in the game.
But injuries to key players unsettled it and Harbour pounced with three quick tries early in the final quarter to hand it a bonus-point 28-5 victory at Watson Park last night.
Despite the advantage of a strong wind, resolute defence from a Taieri side not afraid to run the ball at every opportunity kept the home team to just a 7-0 advantage at halftime.
With the wind at its back, Taieri kept Harbour pinned inside its own half for the greater part of the third quarter. A try to halfback Jack Stewart was just reward for his work in keeping the ball ahead of his forward pack and his service to a dangerous inside-back pairing of Connor Fifita and Kori Rupene.
But an ankle injury to lock Braden Jane, followed soon after by hamstring injury to Fifita, put the Taieri defence into disarray as Harbour ran in three tries in quick succession.
Harbour was well served by openside flanker James Tomkinson, who was tireless both in defence and attack, while Hale T-Pole gave good service at No8, assisting in helping secure good ball from the set piece and creating space for halfback Vinnie Isherwood to set the backs alight.
Lock Chucky Koroi proved an imposing force, often committing three defenders as he ran the ball up. The front row was also a solid trio in set piece for Harbour with loosehead prop Benny Rumble offering stability at scrum time.
Hooker Morgan Buchanan gave T-Pole and Koroi good service at the lineouts.
For Taieri, lock Brendon Murdoch proved inspirational at the breakdown with his ability to retain ball, while Rupene remained a threat in midfield throughout.
University: 48
Green Island: 9
Powerful lock Jack Sherratt played a key role in University's eight-try 48-9 win against Green Island at Miller Park.
Green Island was aggressive, attacked from the start and led 6-0 after four minutes when first five-eighth Ben Patston kicked two penalty goals.
Sherratt lifted the students' confidence when he burst through four tackles on a 35m run to score the side's first try.
That opened the floodgates and the students scored four more tries to lead 29-9 at the break with No8 Sione Teu, flanker Jim Smith and hooker Ricky Jackson dangerous in the loose.
But the game changed in the second spell when Pete Mirrielees, Terry Gough and Matt McCutcheon joined the Green Island pack that camped inside the University 22m for long periods.
The speed and ability of University's backs to break out of their own half led to two more tries in the final 10 minutes.
The best student back was first five-eighth Taylor Haugh with his speed and long passes, Stephen Fenemor gave stability in the midfield and wing Sam McLachlan demonstrated superb skills to squeeze through a narrow gap to score the first try.
Centre Kane Pomare impressed for Green Island.