Zelenko was elected as a Democrat to the Eighty-fourth and to the three succeeding Congresses (January 3, 1955 – January 3, 1963). He was an unsuccessful candidate for renomination in 1962 to the Eighty-eighth Congress.
Zelenko was selected as a Democrat to serve in the Eighty-fourth and three following Congresses (January 3, 1955 – January 3, 1963). He did not win re-election in 1962 for the Eighty-eighth Congress.