MY interpretation is since you will be checking through LAX to SYD all at once (I presume) you present coupons for both LAX-AKL and AKL-SYD at check-in in LAX. However the AKL-SYD u/g probably will not be confirmed until you get to AKL depending on availability.

When is your flight AKL-SYD? (There aren't many biz seats and certain flights have a lot of business traffic.)