The first challenge awaiting the 53-year old coach, who guided his country to the final of the 2012 CAF Africa Cup of Nations, will be helping Niger qualify for their third continental championships.
After getting knocked out in the group phase in 2012 and 2013, Niger, 119th in the FIFA/Coca-Cola World Rankings, missed out on the 2015 edition in Equatorial Guinea.
Zahoui, a former forward for French sides Nancy and Toulon, replaces Gernot Rohr, who quit after failing to qualify Niger for the 2015 Cup of Nations.
The next Africa Cup of Nations will be hosted by Gabon in 2017.