He received a doctorate in theology from the University of Alcalá, and subsequently served in the Jesuit administration in Spain and Italy.
[1] In August 1573, Plaza and fellow Jesuit Diego de Bracamonte met with Juan de Ovando y Godoy [es], president of the Council of the Indies, to discuss the Jesuit missions in Peru.
In letters to his superiors, Plaza expressed doubts about the legitimacy of the Spanish dominion over Peru, questioning the morality of Jesuit involvement in the conquest and colonization.
Plaza praised the mission in his report, writing that the burden on the natives of supporting the priests was ameliorated by a royal stipend, and that the priests did not have to administer corporal punishment to the natives, instead delegating it to a vicar and corregidor.
He served as rector of the Jesuit college in Tepotzotlán, and attended the Third Mexican Council in 1585.