Equatorial Guinea beat Mauritania 3-0 in Malabo on Sunday to end their guests interest in the 2015 Africa Cup qualifiers.
Nzalang advanced to the second knockout round 3-1 on aggregate after reversing a 1-0 loss they sustained in the first leg in Nouakchott on May 17.
Mauritania's exist is a massive blow for Patrice Neveu's side who were hoping to build on the momentum of their 2014 CHAN qualification.
The side's appearance at CHAN this year was the country's first qualification to a major international tournament.
Nzalang will face The Uganda Cranes in the second round in July for a place in September's group stage.