Zanotti was born in Bologna where his father Giampietro was a poet, painter and art historian.

Zanotti studied at Jesuit schools and became interest in science and mathematics, trained under Eustachio Manfredi (1674-1739) at the Bologna observatory where he began to work from 1729.

His contributions included the improvement of instruments at the observatory, the calculation of the elliptical orbit of a comet,[1] maintaining notes on transits of Mercury (May 6, 1752), Venus (June 6, 1761) with which he tried to estimate the distance between the Sun and the Earth as well as the diameter of Venus using parallax based measurements.

He collated an ephemeris and star catalogue along with his assistants Petronio Matteucci and Giovanni Angelo Brunelli from 1751.

He also made predictions on the shape of the Earth including the flattening of the poles based on Newtonian mechanics.