He designed at least 18 original planes, some conversions of landplanes to seaplanes - and a parachute. Other aircraft he produced were named after the engines used, such as the Fizir-Mercedes, Fizir-Wright, Fizir-Titan, Fizir-Kastor, Fizir-Gypsi, and the half-metallic Fizir-Jupiter. His successful designs, almost all wooden, were economic to produce, reflecting the low economic power of the pre-World World War II Kingdom of Yugoslavia, wartime Croatia (Independent State of Croatia) and post-World World War II Yugoslavia, and were highly regarded in Germany and France throughout the 1930s, 40s and 50s.
He had a strong affiliation for trainers and seaplanes, having a vision of connecting the Adriatic islands with a regular seaplane service.
His greatest success was the Fizir FN two-seater with dual controls, over 100 of which were built, which was in use as a trainer up to 30 years after World World War World War II