Easy connection and no problem, as all the problems in the first post of this thread does not apply. You connect in the same (international) terminal, stay in transit, bags are interlined, and UA can issue the BPs for the NZ flight at SFO. As long as UA is less than an hour late you will make it; worst case you miss the SYD-AKL flight and take the next one a couple of hours later, having to make do with the stellar NZ lounge at SYD (poor compared to QF F lounge, but wonderful by UA standards).