Born in Philadelphia to Jonas Phillips and Rebecca Machado Phillips, Zalegman Phillips would emerge as one of the more distinguished member of a distinguished family. His brothers included Naphtali, Aaron and Manuel, and among his sisters was Rachel.
He studied at the University of Pennsylvania, although he never graduated. He then apprenticed with a lawyer, and in 1800 was accepted to the bar, the first self-identifying Jewish lawyer in Philadelphia. Samson Levy, Jr. and Moses Levy accomplished this earlier, and though the sons of a Jew, they were not raised in, nor did they practice, Judaism. Zalegman became the clerk for a Philadelphia court and established his own practice as a criminal lawyer, a firm that would eventually include two of his sons Henry Mayer and Jonas Altamont Phillips.
In 1805 he married Arabella Solomon, daughter of Myer Solomon and Hyah Bush Solomon, and niece of Shinah Solomon Etting. Together they had eleven children.
An avowed Jacksonian, he served as secretary at the first meeting held in support of Jackson in Philadelphia in 1823. Phillips himself entertained the possibility of a life in politics, but when his 1832 congressional bid was unsuccessful, he decided to stick to law and to Jewish life in Philadelphia.
He served as president of Mikveh Israel, and was responsible for the selection and appointment of Isaac Leeser as hazzan. He was instrumental in the construction of a new synagogue building, just as his brother Naphtali was at Shearith Israel in New York.
Despite his Jacksonianism, Zalegman, was a member of a distinguished and old American Jewish family and maintained certain conservative peculiarities. Namely, until his death in 1839, he dressed in antiquated garb, in knee breeches and buckles, with his hair tied back in a queue.