International transfers at SYD are relatively straight forward, if booked on a single ticket. Bags will be through checked. On arrival follow the signs for international transit. If you have reached immigration you have gone too far. Clear security and up one level for departures.

So the issue is the on-time performance and the impact of a misconnect should it occur.

ZQN is an airport surrounded by mountains. While on-time performance has gotten better in recent years, it is still much worse than CHC. I would not book ZQN-SYD-LAX/DFW with such a short connection, unless I was okay with a potential misconnect and forced overnight stay in SYD (due to next available flight being next day).