After his Berlin, Dresden and New York years, Zervas decided to return to Greece in 1937. He was immediately appointed full Professor of Organic Chemistry and Biochemistry at the Aristotle University of Thessaloniki in recognition of his distinguished international work. He stayed in this position until 1939, when he was invited to the Professorship of Organic Chemistry at the University of Athens and also appointed director of the Laboratory of Organic Chemistry of the same institution. He continued conducting research, despite the severe limitations he often faced from the lack of equipment and funding. Concurrent to research, Zervas taught organic chemistry, oversaw the laboratory and guided many generations of young chemists as doctoral advisor for the 29 years he held the post at the University of Athens.
During the Axis occupation of Greece Zervas played an active part in the Greek Resistance as a member of EDES; he was imprisoned twice, first by the Italian and then by the German occupying forces, and his laboratory was destroyed. Following the liberation of Greece, Zervas managed to secure a small part of the American postwar aid for repairs in the University of Athens and the Athens Polytechnic, and thus rebuilt his laboratory in 1948–1951.
In the following years, guided by a sense of personal and professional duty, Zervas voluntarily took on a variety of responsibilities within the Greek state. At his own insistence, he never got paid for these posts and kept receiving only his professorial salary. Some notable positions he held in chronological order until 1968 include:
*Member of the State Committee on Vocational Education (1948–1951)
*Member of numerous committees for the foundation of new industries in postwar Greece (throughout the 1950s)
*First Vice-President of the National Hellenic Research Foundation (1958–1968), of which he was a key founder
*Minister of Industry in the Paraskevopoulos technocratic caretaker government (1963–1964)
*President of the Greek Atomic Energy Commission (1964–1965)
The democratic ideals of Zervas made him a target of the military junta established in 1967, which removed him from his position in the University of Athens in 1968 after almost three decades of dedicated research and teaching. In response, the Academy of Athens of which Zervas had been a member since 1956 elected him as its president in 1970. After his term as President of the Academy, Zervas retired in 1971.