Merzario began his career with Abarth in GT racing and mountain climbs; he also won the Sardinia Rally in 1963 in an Alfa Romeo Giulietta.
Merzario comezou a súa carreira con Abarth nas carreiras GT e nas subidas da montaña e tamén gañou o Rally de Cerdeña en 1963 nun Alfa Romeo Giulietta.