Complex sentence: His close friendship with André Breton and Paul Éluard was instrumental in founding "The Surrealist Group" of Czechoslovakia in 1934 (the first group of this kind outside France), serving as an editor of the group's journal "Surrealismus".
Split into simpler sentences: His close friendship with André Breton and Paul Éluard was instrumental in founding "The Surrealist Group" of Czechoslovakia in 1934. It was the first group of this kind outside France and Nezval served as an editor of the its journal "Surrealismus".