Some genera of polypores produce fruitbodies that grow flat against their woody substrate. Identification from a photo can be difficult or even impossible and this is a pigeon-hole for such polypores that are white(ish).
The zz is there simply to force this group to the end of the alphabetic list of genera/species, since this category would be of no relevance to most users of Canberra Nature Map.
zz flat polypore - white(ish) is listed in the following regions:
Canberra & Southern Tablelands | South Coast