United does not fly to Auckland. Air NZ does; however, it is very stingy in allowing United access to award tickets. Your best bet is to check daily inventory between SYD and SFO/LAX (and vv) to build your itinerary using the multiple destinations mode on united.com. Air NZ is less stingy about allowing United access to Trans-Tasman awards; however, most if not all of these aircraft are single cabin. Flexibility helps; you'll be more likely to get saver inventory on SYD and SFO/LAX during the week and not around holidays.