DR Congo, winners of the inaugural competition in 2009, beat hosts Rwanda 2-1 in the first quarter-final at a sold-out Amahoro national stadium in Kigali.
Iranzi played in Ernest Sugira and the AS Kigali striker fired past DR Congo goalkeeper Ley Matampi for his third goal of the tournament.
Emery Bayisenge had a chance to grab the winning goal for Rwanda in the 89th minute, but his powerful right-footed shot was kept out by a diving Matampi at full-stretch.
DR Congo then took control in extra time, and after two missed opportunities, Botuli Bompunga headed home the winner in the 113th minute to break the hearts of the host nation.
In Butare, the reigning Africa Cup of Nations champions Ivory Coast overcame Cameroon 3-0 in an all-West African quarter-final. After a goalless 90 minutes, second-half substitute Koffi Boua broke the deadlock five minutes into extra time.
Two other goals from Atcho Djobo (102) and Serge N'Guessan (112) were enough to send the Elephants into the last four where they'll meet either Tunisia or Mali next week.