He was the founder of the Barnabites and a promoter of the Passion of Christ, the Eucharist and the renewal of the religious life among the laity.

There, he became a member of the Oratory of Eternal Wisdom,[5] where he met Bartolomeo Ferrari and Giacomo Antonio Morigia.

Their devotions mainly focused on the teachings of Paul of Tarsus with emphasis on love for the Eucharist and Christ crucified.

They instructed in the rudiments of their faith, gave missions in parishes in the city and elsewhere, and cared for the sick in the hospitals.

In 1533, having received encouragement from Pope Clement VII, Zaccaria took a small house near the church of St. Catherine at the Ponte dei Fabbri, and here they began their community life.

[6] In 1534 at St. Catherine's, he popularized the Forty-hour devotion for the laity – the solemn exposition of the Blessed Sacrament for adoration by the faithful – accompanied by preaching.

In July 1537 Zaccaria accompanied the first Pauline missionaries (Barnabites, Angelic Sisters, and Laity of St. Paul) and some collaborators (Castellino da Castello and Fra Bono Lizzari) to Vicenza to open the congregation's second house.

In June Zaccaria writes to the couple Omodei in Milan and speaks of a great "weariness of the body."

Anthony Zaccaria died on Saturday, 5 July 1539, at the age of 36, at three o’clock in the afternoon, in the house where he was born, in the arms of his mother and surrounded by his first companions.

[4] He was buried in the San Paolo Convent of the Angelics of Saint Paul, the female branch of the Barnabites, in Milan.

On 15 January 1535 Pope Paul III approved the Angelic Sisters with the Bull, Debitum pastoralis officii.

[9] In art, he is depicted wearing the black cassock of the Order and holding a lily, cross, chalice and/or a host.

In addition, there is a twelfth letter: though it bears only Negri's signature, it was without a doubt penned by Anthony Mary.

One (Letter VI) is addressed to Bartolomeo Ferrari, but it is meant for both Barnabites and Angelics who were doing missionary work in Vicenza.

The last three letters, a remarkable total of 2,200 words penned in the brief space of ten busy days, were addressed to an Angelic, a Barnabite, and a Married Couple.

Written respectively on 10, 11, and 20 June 1539, that is, within less than a month of his death, these letters unwittingly became, as it were, his final testament to the three families of his foundation.

Early Barnabite historian, Father Giovanni Antonio Gabuzio, retrieved it during his stay in that city from 1584 to 1595.

Later on, as a priest in Cremona, he wrote in it the talks on the Ten Commandments, which he gave at the Amicizia Oratory in Saint Vitalis Church.

The Sermons are addressed to noble laymen, who were married and had children, and were active members of the Amicizia Oratory, in the years 1529-1530 when Anthony Mary was a priest; however, their content is applicable to everyone.

Recently, a hypothesis was put forth, saying the Sermons are not liturgical homilies but opening talks given at the Amicizia Oratory meetings, where all present could then speak.

This change of style helps locate Anthony Mary's interpolations in the original text of Battista da Crema.