A bit of heavy breathing going on here! The clock is ticking on getting this things booked before year's end.
On the M&M site, things go a bit haywire when trying to price the itinerary up on days where there is definitely availability in 1st on the LX flights from ZRH to LAX. Is this normal? Trying to price up DUS-ZRH-LAX and vv in 1st simply doesn't work, the LX option is not offered on the outbound (even though it works when doing dummy bookings as one ways).
Making it into a sort of open jaw itinerary, ZRH-LAX and LAX-ZRH-DUS as a round trip, yields about EUR468 taxes, expensive but not as bad as I expected. Pricing it as ZRH-LAX and LAX-ZRH comes out at EUR461, some 8 Euros. Wonder why the site won't price the whole thing on LX from DUS. Could it be a married segment issue?
It would seem that booking the trip as two One Ways makes the taxes a whole lot more expensive, totaling nearly 700 Euros when added together.