Classical Cepheids (DCEPs) are the most important standard candles in extra-galactic distance scale thanks to Period-Luminosity ($\rm PL$), Period-Luminosity-Color PLC$) and Period-Wesenheit PW$) relations that hold for these objects. The advent of {\it Gaia} mission, particular Early Data Release 3 (EDR3) provided accurate parallaxes calibrate relations. In order fully exploit measurements, ze...