[2] Zahra's career as an artist lasted for four decades, and he came to be considered as the greatest painter from Malta of the 18th century.

Zahra became the most prolific Maltese painter by around 1745, being rivaled by the French artist Antoine de Favray who at that time worked in Malta.

Zahra's style further developed over the years, and in around the mid-1750s his figures and the atmosphere of his paintings had changed, showing influences from Mattia Preti and Favray himself.

[4] Zahra's first significant commission came in 1732, when he painted an altarpiece depicting Three Dominican Saints Adoring the Holy Name of Jesus for the Church of Santa Maria della Grotta in Rabat.

Works by Zahra are located in St. Paul's Cathedral, Mdina, the Cathedral of the Assumption, Gozo, the parish churches of Attard, Balzan, Birkirkara, Floriana, Għarb, Għargħur, Għaxaq, Gudja, Lija, Marsaxlokk, Mosta, Naxxar, Qormi, Rabat, Senglea, Siġġiewi, Sliema, Tarxien, Valletta, Victoria, Xagħra, Xewkija, Żabbar, Żebbuġ, Żejtun and Żurrieq, along with numerous other churches and chapels.