A powerful strike early in the second half from Helder Pelembe handed Mozambique a narrow 1-0 won over Gabon in the first leg of their World Cup qualifier in the Mozambican capital on Wednesday.
It leaves the tie still delicately poised with the return set for Saturday but Zambia made a big stride in their bid to reach the next round with a 1-0 away in Sudan.
The two matches were the first in a busy six days of games across the continent as Africa plays a second round of knockout matches to cut down the World Cup field to 20 counties ahead of the start of the last group phase next year.
Winston Kalengo scored a 26th minute goal to see Zambia win 1-0 in the provincial town of Karima, on the banks of the River Nile, and take a major advantage into the return leg at home in Ndola on Sunday.
Gabon struck the woodwork in the first half but were under pressure for most of the encounter.
Pierre-Emerick Aubameyang did not feature for Gabon, said by officials to be injured despite a goal and almost 90 minute outing at the weekend for Borussia Dortmund in the Bundesliga, but FIFA presidential election candidate Gianni Infantino, the UEFA general secretary sat in the VIP section on a charm offence to the Mozambican federation.