Hi
I'd be careful with basing your choice of carrier and route solely on the ZED principle as its a concept that isn't as entrenched among European carriers as it is with N. American airlines. Speaking for LH, they'd also accept a ticket issued for PDX-FRA on the SFO or LAX to FRA route as theses cities are all on the west coast, so the ID ticket fares are all the same. Your best bet may be to have back up tickets for each alternative with the respective carrier endorsed on the ticket. Nonetheless as you're flying out of the USA, those European carriers, or moreso their staff, may be more in tune with the whole ZED process.