When scheduling uses the code "Fz" it means more than "frozen" or "no trip trades accepted".

It means they want to generate interest in said pairing by letting everyone see it. Scheduling has the ability to mask pairings they are building and not have them show up, don't let them tell you otherwise. They do this with trips that are open in the assignment window.

This way you will check open time to see if it's still frozen and take it off their hands when it's ready for pickup by a crewmember, standards or training scheduling.