Cameroon punished Zambia's poor defending to bounce back to winning ways and show they are still genuine Africa Cup of Nations contenders.
A Geremi free-kick gave Cameroon the lead, and Joseph Desire Job and Achille Emana added goals before the break, both after defensive errors.
Samuel Eto'o's penalty equalled the Nations Cup goalscoring record.
Shoddy defending gave Job his second and Cameroon their fifth, and Chris Katongo got Zambia's consolation goal.
The 14-goal tally of Laurent Pokou of the Ivory Coast has stood for 28 years, but Eto'o will surely surpass it, with Cameroon looking likely to go beyond the group stage.
Making five changes to the team that lost 4-2 to Egypt in their opening match, the Indomitable Lions began with a spell of attack.
But Zambia also had chances, and James Chamanga came close with a long-shot on 25 minutes.
A minute later Cameroon went ahead, as Geremi's free-kick in front of goal just outside the penalty area curled inside the left post.
606: DEBATE
In the 31st minute it was 2-0, thanks to embarrassing defending by Zambia.
Kennedy Nketani missed as he tried to head a long ball away, Billy Mwanza also missed has he attempted to clear, and the ball fell to Job, who only had to stroke past the goalkeeper.
Eto'o had a quiet first half, but almost scored on 40 minutes when his ferocious volley whistled over the crossbar.
Two minutes before half-time, another defensive blunder gifted Cameroon a goal.
Alexandre Song threaded a ball through which Isaac Chansa failed to deal with, and Achille Emana rounded Mweene to make it 3-0.
Cameroon sat back as Zambia attacked in the first 20 minutes of the second half.
But the Indomitable Lions went further ahead with Eto's spot-kick.
The Barcelona striker fired a free-kick into the Zambian wall, and Billy Mwanza handled.
The penalty was then calmly slotted into the bottom-left corner.
Three minutes later, Zambia's hard-working captain Chris Katongo unleashed a fierce shot that went just over the bar, with goalkeeper Carlos Kameni at full-stretch.
Katongo headed onto the crossbar with 15 minutes remaining, Clive Hachilensa then had a shot cleared off the line, and Jacob Mulenga had a shot parried over by Kameni.
But another defensive howler made it 5-0, when Clive Hachilensa headed the ball into the path of Job, who walked the ball into the net.
A minute from time, the Chipolopo finally got the consolation goal they thoroughly deserved, with Katongo sliding home a cross.
The scoreline was not a fair reflection of the game, but Cameroon proved that they remain a class act.
Cameroon: Kameni, Binya (Nkong 63), Song, Atouba, Bikey, M'Bami (Makoun 67), Geremi, Emana (Idrissou 77), Song Billong, Eto'o, Job.
Subs Not Used: Hamidou, Mbarga, Tchato, Angbwa, Epalle, Essola, Mbia, N'Guemo, Tomou.
Goals: Geremi 28, Job 32, 82, Emana 44, Eto'o 66 (pen).
Zambia: Mweene, Nketani (Himonde 38), Musonda, Mwanza, Hachilensa, Chansa, Bakala (Njovu 83), Felix Katongo, Jacob Mulenga, Christopher Katongo, Chamanga (Sunzu 64).
Subs Not Used: Kakonje, Poto, Chinyama, Kampamba, Kalaba, Kasonde, Clifford Mulenga, Phiri, Mayuka.
Goals: Christopher Katongo 90.
Ref: Yuichi Nichimura (Japan)
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