The same year he ceased his professional activities and traveled across Europe before he returned and organized the food supply of Zagreb during World War I.

[1] Heinzel was also an early automobilist, who along with Ferdinand Budicki drove the first car in Zagreb, and was one of the founders of the Croatian automobile club in 1906.

[5] During the Kingdom of Serbs, Croats and Slovenes, Heinzel was first elected mayor in 1920 and served until the August 1921, when the city administration was temporarily disbanded.

[1] His administration organized the construction of large sections of today's Peščenica, Trnje, Trešnjevka, Maksimir and other city neighborhoods.

[4] Heinzel's efforts came at a considerable cost, however, as the city had to take out a loan of 250 million Yugoslav dinars, a topic of much criticism at the time.