Ziel Feldman is the founder and managing principal of HFZ Capital Group, a real estate investment and development company focused on Manhattan real estate and formed by Feldman in 2005. Among the marquee projects HFZ has been involved with are 11 Beach Street, One Madison at 23 East 22nd Street, 11 East 68th Street, Halcyon at 305 East 51st Street. Feldman's HFZ specializes in condominium conversions.

Feldman began his career as a real estate attorney and multi-family property investor in 1984. In 1991 he co-founded Property Markets Group. Over the course of his career, Feldman claims to have bought, sold, or developed over 10,000 residential units and acquired, managed, developed and then sold over $6 billion in assets.

In 2013 Feldman's HFZ paid over $600 million for Westbrook Partners four-building, 750-apartment Manhattan real estate portfolio, which included 295 Madison Avenue, 444 Madison Avenue and the Astor at 235 West 75th Street.

In 2016, HFZ  revealed plans for a pair of residential buildings along the High Line at 76 Eleventh Avenue. The Bjarke Ingels' designed project was dubbed "The XI" and HFZ hoped to sell more than $2 billion worth of condos there. But the firm's financial troubles during the COVID pandemic stalled the project in 2020.

HFZ's lenders seized control of several other condo projects, as well as a 12 million-square-foot last-mile industrial portfolio, as the firm fell behind on payments and faced a cascade of lawsuits.