The 31-year-old converted two penalties in a 3-1 victory over Vipers of Uganda that overturned a 1-0 away loss in the last-32 tie.
Ndumiso Mabena doubled the lead from a fiercely struck free-kick before half-time in northwestern mining town Rustenburg.
Milton Karisa scored for Confederation Cup debutants Vipers on 55 minutes to nudge his club in front on the away goal rule.
Mzimela had the final say, however, converting another penalty a minute into stoppage time to rescue the South African club.
Ulinzi Stars of Kenya overcame having a player sent off to whip Smouha of Egypt 3-0 in Machakos, but still exited the African equivalent of the Europa League.
Smouha advanced 4-3 on aggregate having built a commanding first leg lead in Alexandria last weekend.
Samuel Onyango scored twice in the opening half for the Kenyan armed forces side, who were reduced to 10 men on 55 minutes when John Kago was red-carded.
Undaunted, Ulinzi grabbed a third goal 13 minutes from time through Omar Mbongi and rattled Smouha survived several late scares.
Kenyans Jesse Were and David Owino scored for Zesco United of Zambia, who booked a play-offs place by drawing 2-2 with Le Messager Ngozi of Burundi in Bujumbura.
Leading 2-0 from the first leg, Zesco equalised twice in the return match with Owino scoring in the final minute.
JS Kabylie of Algeria, the most decorated club in the last-32 field with six CAF titles, left it late to eliminate Etoile of Congo Brazzaville.
The only goal of the tie came a minute from time in northeastern city Tizi Ouzou with Mohamed Boulaouidet rifling a free-kick into the net.
Moroccan sides MAS Fes, the 2011 Confederation Cup winners, and Ittihad Tanger progressed in contrasting ways.
Fes took a 3-1 lead over SC Gagnoa to the Ivory Coast, where they lost 1-0 to a Martin Kossivi goal midway through the second half.
Ahmed Hamoudan scored a hat-trick as Tanger triumphed 3-0 in Morocco against Kaloum of Guinea, who won 1-0 at home.
Recreativo Libolo of Angola held Ngezi Platinum of Zimbabwe 0-0 in Harare to advance having built a 2-1 first leg advantage.