It is not known just when or where Saint Zenon and Saint Zoilos lived, but according to the Byzantine verse Synaxarion, they died while living in the world (Paris. Coislin. 223, from the year 1301).1
The names of Saint Zenon and Saint Zoilos and a couplet composed for them were included in the Greek Menaion (printed in Venice in 1596) and in the Synaxaristis. When the Greek Synaxaria were translated into Slavonic, their names and the couplet in their honor were included in the various Prologs. From there, they were incorporated into the Great Reading Menaion (Великие Минеи Четии) for March, and into the modern calendar of the Russian Orthodox Church.
The couplet reads: "Released from this life, Zenon and Zoilos went forth to a better life" (literally "existence").
1 Le fonds Coislin is a collection of Greek manuscripts acquired by Pierre Séguier, but named for Henri-Charles de Coislin, its second owner. It is now held in the National Library of France.