For AKL-LAX I try to stay awake the first 3-4 hours of the flight and make sure I get woken for breakfast before landing. This usually means I've managed 5-6 hours sleep and reasonably awake when in transit in LAX. Avoid caffeine in transit or early part of LAX-LHR. For LAX-LHR I'll stay awake the first part of the flight and then sleep another 3 hours or so before landing. Be active (or if onward flights make sure not to sleep during them) and by night time I'll be nicely exhausted = sleep and adjusted to Europe time zones.

For LHR-LAX try to stay awake as much of flight as possible, usually sleep a couple hours before landing. Then LAX-AKL a long sleep. If stay awake for supper meal service end up with about 6 hours sleep due to noise serving breakfast, if sleep straight away then get good 8 hours.