Lomu made his first start for over three years as Harbour sealed second place in their group, behind neighbours Auckland.
The 31-year-old's former province Wellington finished in third spot in the group after a 39-25 triumph over Tasman.
Pool B winners Waikato overcame Stephen Donald's sending-off early in the second half to defeat Northland 42-21.
Canterbury's 14th successful Ranfurly Shield defence was earned by a 32-16 win over Counties-Manakau at Jade Stadium.
The victory moved them ahead of Otago to take second place in the group, and boost their second-round seeding.
The top three teams in each pool will play off for top seeding in the quarter-finals.
Elsewhere, Bay Of Plenty defeated Taranaki 20-16 and Southland overcame Hawke's Bay 15-11.
The second-round fixtures, which are likely to see the implementation of midweek rugby for the first time in New Zealand, will be confirmed on Monday.
The winners of two repechage groups will join the top six teams in the last eight.