Peter holds a Master in Architecture from the Harvard University Graduate School of Design and a Bachelor of Architecture with First Class Honors from the Royal Melbourne Institute of Technology in Australia. He has held visiting professorships at UC Berkeley, the University of Southern California, Florida International University, the Ecole Spéciale d'Architecture in Paris, the Institut für Städtebau und Raumplanung (Institute for Urban Design and Urban Planning) at the Universität Innsbruck, Austria and the Royal Melbourne Institute of Technology in Australia.
Zellner was the 2013 Ivan Smith Eminent Chair at the University of Florida, School of Architecture. Zellner taught design and theory as a faculty member at the Southern California Institute of Architecture (SCI-Arc) from 1999 to 2015 where he coordinated the school's Future Initiatives Urban Design program between 2008 and 2014. In the fall of 2016, Zellner founded the Free School of Architecture, a tuition and salary free, not-for-profit organization.
In the fall of 2019, he served as the Brown-Forman Visiting Chair in Architecture at the University of Kentucky College of Design.