Activate Coretapper's first ability by tapping it, putting a charge counter on Magistrate's Scepter.
Activate Urza by paying ({6} magic symbol) , creating a token copy of Coretapper that is a 1/1 Soldier.
Activate the token Coretapper's second ability by sacrificing it, putting two charge counters on Magistrate's Scepter.
Activate Magistrate's Scepter's second ability by tapping it and removing three charge counters from it, causing you to take an extra turn after this one.