Unfortunately, in Flash you cannot create a hierarchy of masks on the same timeline, so you will have to work around that limitation.
Since the facial oval is probably the more important mask you need to convey the desired 2.5D look, you can use patching for the eyes, or keep the eyes outside of the face mask.
Another option would be to have the eyelids and pupils nested internally to the eye symbol - then you can use masking in there, and mask the eye as a whole with the facial oval mask.
Have a look at the sample Bunny file - TP Sample button
in SMR Helpers - included with your installation to see how we treat the bunny's eyes.
Just a side note: From your picture it looks like the facial features are not nested inside the head symbol, but rather they are all floating on the Main timeline.
Put them inside the head and run that as a synced timeline - this will be your REF and ANM for TransPosing.