There is only one Catholic church on island of Zakynthos, where masses are celebrated. Masses (updated: 06.2018) are every Sunday at 10:00 and 19.00 and every Saturday at 19:00. The schedule sometimes cen change and updated, it can always be found at the bottom of this page: http://www.catheclpatra.gr/
The church is located in the Zakynthos City (capitol of the island) near St. Mark's Square (Agiou Markou). Square is easy to find, because it's like an extension of the largest square in Zakynthos, Solomon's Square (Agios Solomonos)
Masses are celebrated by a priest, who is Italian, but the Mass is celebrated fragmentary in English, Greek, Italian, Latin. It is interesting, that the sermon is spoken firstly in Italian and second time in English.
In the church there can be found many readings and many Christian songs lirycs in several languages, including English, German, Italian, French and Polish.