Mizzi was appointed as Sliema coach last June.
According to various reports, an Italian company that is about to buy a large share of the club triggered the resignation.
Physical trainer Renzo Kerr Cumbo and the goalkeepers coach have also resigned from their position at the club.
Reports suggest that the new full time technical director will be headed by Sports Director Roberto Causio.
The new coach will be Alfonso Greco.
The new assistant coach, physical trainer and goalkeeper's coach names still have to be announced.