I have found a way to fly without a mount yet again not just no animation but you can fly anywhere even inside buildings
Step 1: Put on a Skeletal Costume :Not sure of what others work: (also may work with anything else that says you cannot mount while shape shifted and zen-flight permits flying)
Step 2: Go into a different zone via cross-realm while on a zen-flight cloud with the costume on
Step 3: Fly without a mount and enjoy
you can also cast spells while flying without falling