You know you are only allowed 2 stopovers in the continent of origin (so 1 of the 3 LHR arrivals will have to be a transit, with less than 24 hours in LHR). The routing looks legal otherwise (CX is now allowed to SGN but not on the Air Vietnam codeshare, which might restrict your travel dates). SFO-YVR is highly seasonal -- this is the first year for the route, next year hasn't been announced and it may not be continued, and it is operating for only a few weeks this year. So unless you happen to be flying SFO-YVR within the next 2 months you won't be able to book that (and there is no AA service SFO-YVR as AA codeshares on AS is not allowed). You may have to drop SFO-YVR from the routing in order to get this issued, if you aren't within the dates for this flight. Finally NOU-SYD in J tends to be sold out, so might have to be pretty flexible on dates, similarly for SYD-AKL on LA (there are only 20 F seats per week on this route, and they are kept for sale SYD-SCL, so don't expect to be able to book this in A more than a day ahead, and it may take a few weeks to actually get 2 seats on this flight ... most likely you will be flying D on QF on this route).