The AKL-JFK flight arrives at 14:25. Plenty of time to connect to one of the evening flights to LHR, so I suspect there's no layover.
I can't get the AA website to sell that itinerary as a basic economy ticket (only "regular" economy, which includes one checked bag), so this could be a ticket booked through a low-cost TA. It may include an overnight layover if breaking it up that way leads to a cheaper ticket.