Zambia are seeking to banish the ghosts of the last 16 years by reaching the African Nations Cup semi-finals for the first time since 1996.
But opponents Sudan can ensure another in a long list of surprise results at the tournament, co-hosted by Equatorial Guinea and Gabon, if they are to progress to the last four.
The two teams meet in Bata on Saturday in the first of four quarter-final ties this weekend.
Zambia, who finished top of Group A, start as runaway favourites after imposing with their fast-paced game, well-organised midfield and disciplined defence.
Under French coach Herve Renard they have rediscovered a spring in their step, missing in the qualifying competition, and reached the last eight for a second successive tournament.
But Sudan's ability to spring a surprise result is all too evident, with their team growing in confidence even after sneaking through to the last eight on goal difference from Angola.
They scored counterattack goals in their last match against Burkina Faso, where their 2-1 win was the first in the finals for 42 years, pushing them to four points and a place in the quarter-finals.
In a sense they have nothing to lose - their place in the knockout stages already exceeds expectations -- and they can patiently wait to catch Zambia in the game.
"Zambia are a fast, well organised team which has achieved good results here and we must prepare tactically and physically for them," said coach Mohamed Abdallah.
Zambia are expected to stick with the attacking form that has seen off both Senegal and Equatorial Guinea in the early rounds. Striker Emmanuel Mayuka and winger Chris Katongo both have scored twice.
"You just have to fight for the flag you represent and for the national colours you wear," said Renard to his players in the wake of the explusion from the squad of winger Clifford Mulenga, a fringe player who had gone out partying in defiance of a curfew.