William Zeckendorf

520 Park Avenue (Instagram via Tal Alexander)

Penthouse at 520 Park Avenue sells for $35M — $8M below ask

Zeckendorf building’s highest full-floor residence trades in off-market deal

People who made NYC: The legacy of William Zeckendorf Sr.

People who made NYC: The legacy of William Zeckendorf Sr.

740 Park Avenue and William Lie Zeckendorf (Credit: Wikipedia and Getty Images)

Zeckendorf sells co-op at 740 Park Ave for $29.5 million

The developer bought the unit in 2011 for $27 million