Dual active bridge converter
I suggest you determine load condition you want to evaluate efficiency (losses) as ZVS operation depends on the phase shift which effects the RDson. Ony one leg with see ZVC - the other may or may not see ZCS.
Regarding RDson -  I always assume the junction to be at 100C so the RDson is 2x the stated spec at 25C.
I assume you are controlling the output stage as a synchronous rectifier - correct?
If so then you can simply use the RDson for those FETS but if not then the loss is much higher as the body diode is in play (Vdrop*I).
Hope that helps somewhat.