Neither side could find the net in the opening period of the first-leg clash, but Zerdab came up with the goods three minutes before the hour mark to send the Algerian outfit into the second leg with a one-goal advantage.
CS Constantine reached this stage with a 4-3 aggregate victory over Nigelec of Nigeria, while Liberian strugglers Red Lions were playing their first match of the tournament after preliminary round opponents Estrela de Cantanhez withdrew.
In Friday's other clash, Kondzo and Bayelsa United played out a goalless draw to leave the tie wide open ahead of the reverse fixture.
Nigerian side Bayelsa could be forgiven for feeling rusty, having not played a competitive game since the end of their domestic season in October
The second legs of each tie will be played next weekend, while there are a number of other first-leg matches this Saturday as 12 more teams look to give themselves a fighting chance of reaching the next round.
‘After Manchester City’s recent form, maybe they’re the underdogs against Manchester United!’ Former Red Devils defender on this weekend’s derby
‘Arteta, Alonso, Emery, me… none of us were physical players – we needed the understanding of the game. That probably helped us move into management’: Premier League boss reveals reasons for natural career progression
