I always think it's worth talking to an EXPERT Travel Agent in cases like this. Trailfinders have a Dublin branch.
Question. Does New Zealand have to be a side trip? If you could continue from BNE to NZ then to SFO it might be more "efficient" fare wise.
Lastly, despite what I just said, here's an off the wall suggestion. The Air New Zealand round trip to Auckland allows stops in Hong Kong and on the west coast of the USA. A few years ago I went London/Hong Kong/Auckland/San Franciso drove the coast and then Los Angeles/London. So go to Auckland with your stop in HKG then buy a separate ticket a couple of days later back to Brisbane, come back to NZ and then continue across the Pacific. You could make your way from Auckland to Wellington before you fly to Brisbane and then fly back to somewhere on South Island to see the South, hop to Auckland and then pick up the San Francisco flight. You would have to find your own way from San Francisco to Los Angeles. Oh and car companies in New Zealand count all your days towards a cheaper hire so the fact that you might have a week then a break and another week should get you a 2 week rate. Try Apex. Actually they also included the cost of our ferry from Picton to Wellington "free". Air NZ is a good little airline - you might even want to consider their Business Class.