During this time the UPD splintered into ethnic/regional factions led by Apithy, Hubert Maga, and Justin Ahomadégbé-Tomêtin.

Zinsou merged the remainder of the UPD with Ahomadégbé-Tomêtin's Bloc Populaire Africain to form the Union Démocratique Dahoméenne.

While a senator, Zinsou developed a close bond with future President of Senegal Léopold Sédar Senghor.

Zinsou was a deputy to Dahomey's Territorial (later National) Assembly and was Minister of Commerce during the "loi-cadre" liberalization period of 1958 to 1959.

He did not want to see the breakup of France's African colonies after independence and was the secretary of the Dakar-based Parti du Regroupement Africain (PRA).

Zinsou was again foreign minister from late December 1965 to 1967 in General Christophe Soglo's administration.

As President, Zinsou promoted anti-smuggling policies, countermeasures against strikes, and a more efficient tax collecting system.

[5] On 16 January 1977 an attempted coup d'état took place in Benin with a group of armed men led by renowned French mercenary "Colonel" Bob Denard.

[8] Zinsou, like other world leaders of the time, contributed to a disc left on the surface of the Moon by the astronauts of Apollo 11.