During the final years of Francoism Zamanillo engaged in the launch of a broad Traditionalist organization. Following the so-called Ley Arias of December 1974, which legalized political associations, he first tried to mobilize support by means of a new periodical, "Brújula", gathering together "partidarios de la Monarquía tradicional, social y representativa". In June 1975 the initiative materialized with 25,000 signatures required as Unión Nacional Española; Zamanillo entered its Comisión Permanente and in early 1976 jointly with Gonzalo Fernández de la Mora its presidency, becoming also member of Junta Directiva. The association, in 1976 officially registered as political party, adhered to Traditionalist principles; Zamanillo explained its objectives as "lo que hay que hacer es un 18 de julio pacífico y político", played down differences with other right-wing groupings and advanced suggestions of a National Front, formed by UNE, , and others. In May 1976 he co-organized Traditionalist attempt to dominate the annual Carlist Montejurra gathering, since mid-1960s controlled by the Hugocarlistas; the day produced violence, with two Partido Carlista militants shot.