The epic of Shahnameh discusses various kings before Alexander conquered Persia which don't match with the names associated with Achaemenid kings. Some sources refer to this mythical empires as Pishdadian and Kayanian but I couldn't find much else on these names.
Are these used to distinguish the ancient Persian empire from the mythical ones discussed in Shahname and other epics or do they actually refer to different periods of Achaemenid and the nonmatching names are due to lack of reliable sources at the time Shahname was being written?