The harmonious integration of his buildings in the surrounding urban landscape proves Vorhoelzer's ability as a city planner.
With the beginning of the Third Reich he lost his chair accused of being an "architectural bolshevist", although he resumed working as an architect and, for example, built the church "Mary Queen of Peace" in Obergiesing (1936–37).
On the eve of World War II, Vorhoelzer emigrated to Turkey, from where he has been expelled in 1941 due to an allegation of espionage for Germany.
In the post-war debate on the reconstruction of Munich, Vorhoelzer pointed out that parts of the city had been in need of rehabilitation even before the war.
He called for a radical new development plan, in which Flachbauten low-rise and high-rise buildings played an important part.