ZRH-ATH is an European flight. According to swiss.com's special meals page:
"The service is available in any flight class on long haul flights, and in SWISS Business on selected European flights."
Unfortunately it's not clear which European flights offer the service. I suggest you contact LX's customer support by filling out an online form rather than phoning them.
https://www.swiss.com/ch/EN/customer...ng-reservation