Could it be a storage / maint. location
I'm stilling here in LAX an just noticed UA 9958 is going to VCV at 9:45 p.m. This is the same type of situation (all of the other listings have a city name, not the code). A quick search revealed that this is where they store planes that are not in use and also a location for aircraft painting. Is it possible that ZZF is a location where similar functions are performed for EK or just a code for planes that are going into maint. at DBX?