If Wydad Casablanca of Morocco defeat visiting ASEC Mimosas of Ivory Coast on Sunday in Group A, Wydad and Zesco will qualify for the semi-finals of Africa's premier club football competition.
Zesco have eight points, Wydad seven, Ahly five and ASEC four in a mini-league where head-to-head records count in the event of a tie.
Ahly, who needed maximum points to keep up their hopes of progressing, dominated possession for much of the match in  Alexandria.
But Zesco, looking for a first semi-finals appearance, were quick on the counter-attack, and frustrated the Egyptians who are managed by former Tottenham boss Martin Jol.
Kenya's Jesse Were took advantage of slack marking to nod the Zambians into a sixth-minute lead with  Rami Rabia levelling on the half hour.
Were struck again five minutes later, hitting the ball across goalkeeper Ahmed Adel into the far corner.
Veteran striker Emad Meteb was brought on in the second half and snatched an 85th-minute equaliser for the Egyptians.
His penalty area bicycle kick deflected off Kenyan David Owino, leaving goalkeeper Jacob Banda stranded.
The result means that a semi-final place could be secured for Zesco and Wydad Casablanca, if Wydad can beat ASEC Mimosas on Sunday.
Wydad, coached by Wales-born former Real Madrid manager John Toshack, want to get back on the winning trail in Rabat.
They have taken only one point of a possible six off Ahly after beating ASEC and Zesco.
The loss of form by star striker Reda Hajhouj must be a worry as he has fired four straight blanks in group matches after scoring six goals in six qualifiers.
Since shocking Ahly in Alexandria, 1998 champions ASEC have faltered, losing away and drawing at home against Zesco.
Mamelodi Sundowns of South Africa have won Group B thanks to three consecutive victories, leaving Zamalek of Egypt and Enyimba of Nigeria to fight for the second semi-finals spot.
Five-time African champions Zamalek beat Enyimba away and one point from the return match in Cairo Sunday will guarantee their progress, if only on head-to-head records.
Record eight-times African champions Al Ahly of Egypt are facing elimination from the 2016 African Champions League after being held 2-2 at home by Zesco United of Zambia.