Lookman struck after 36 minutes against Cameroon in Abidjan and clinched a 2-0 last-16 victory for the Super Eagles by finding the net again in the final minute of regular time.
Dala took his goal tally to four — one less than 34-year-old chart-topper Emilio Nsue of Equatorial Guinea — by scoring twice before half-time in a 3-0 victory over Namibia in Bouake.
Nigeria, among the title favourites with a line-up including African player of the year Victor Osimhen, and outsiders Angola clash next Friday for a semi-final place.
In Abidjan, Nigeria thought they had taken an early the lead only for a Semi Ajayi goal to be ruled offside after Cameroon failed three times to clear a corner.
Although they had less possession, the Super Eagles looked more likely scorers than the Indomitable Lions and did go in front on 36 minutes.
Oumar Gonzalez failed to control a throw-in and lost possession to Osimhen, who charged goalwards and set up Lookman, whose shot was fumbled by Fabrice Ondoa before entering the net.
Another incident of careless Cameroon defending, early in the second half, ended with Christopher Wooh conceding possession, then fouling Lookman on the edge of the area.
Lookman unleashed a hard, direct shot from the resulting free-kick, but it was just too high.
Nigeria goalkeeper Stanley Nwabali retired injured after 78 minutes to be replaced by Francis Uzoho while fit-again star Cameroon forward Vincent Aboubakar came off the bench.
After defending in depth to maintain their slender advantage, Nigeria won a free-kick which led to Lookman sealing victory.
Calvin Bassey crossed and Lookman got to the ball first in the goalmouth. Ondoa did get his hand to the shot, but could not stop it entering the net.
‘Fear no team’
Angola captain Fredy, who created both Dala goals, dedicated the triumph over Namibia to the people of the southern Africa country.
“Economically, times are tough for many Angolans so I hope our victory has lifted spirits back home.
“We are in the quarter-finals having come to Ivory Coast as outsiders. That rating was hardly surprising as only Tanzania and the Gambia were ranked lower among the 24 contenders.
“But being written off by many observers motivated us. We believe in our abilities as footballers and are raring to go against Nigeria.
“Once again we will be the underdogs and once again we will be determined to prove the forecasters wrong. We are proud Angolans and fear no team.”
After Dala scored twice, Mabululu netted midway through the second half to effectively end as a contest the clash of southern Africa neighbours.
Both teams were reduced to 10 men by first-half red cards with Angola goalkeeper Neblu and Namibia defender Lubeni Haukongo sent off.
Neblu — one of many Angolans who use a nickname rather than their real name — handled a Bethuel Muzeu lob outside his area and was immediately red-carded on 17 minutes.
After a water break to assist players performing in searing 34 degrees Celsius (93 Fahrenheit) heat, the match took a dramatic turn with two goals and another red card in four minutes.
A Gilberto cross and Fredy cutback set up Dala to sidefoot the ball into the corner of the net on 38 minutes.
Namibia surrendered their numerical advantage two minutes later when Haukongo was yellow-carded a second time and sent off.
Dala struck again on 42 minutes, powerfully heading a Fredy free-kick into the corner of the net to give Angola a two-goal advantage.
After early second-half pressure from Namibia came to nought, Angola stretched their lead on 66 minutes.
Veteran Mabululu sprinted on to a Dala pass before superbly curling a shot past goalkeeper Lloyd Kazapua.
