In 1943 and in 1946 he was invited in Zurich by Rudolf Fueter, in order to present his researches: later and during all his career he lectured in almost all Italian and foreign universities.

During one of their meetings, lasting a little more than two hours, Martinelli taught him Élie Cartan's theory of exterior differential forms, and Rizza used successfully this tool in his first research works.

Guido Castelnuovo, Federigo Enriques, Enrico Bompiani, Tullio Levi-Civita Mauro Picone and Antonio Signorini were all working at the Sapienza University of Rome when Enzo Martinelli was a student there, following their lessons: Zappa (1984) describes the activity of the institute of mathematics during that period as extremely stimulating.

[29] Another central aspect of his personality was a deep sense of justice and legality:[6] Martinelli was very careful in performing his citizen and university professor duties, and he was also ready to fight for his own rights and for the needs of higher education.

Concerned by the growing interference of bureaucracy in university education, already in the 1950s he was heard by Rizza (1984, p. 6) complaining that: "In Italia mancano le menti semplificatrici".

[31] In the same period, while performing his duties as the director of the Guido Castelnuovo Institute of Mathematics at the Sapienza university of Rome, his rare intellectual honesty[32] and rigorous rationality, according to Rizza, caused him troubles when dealing with many who "believed in everything except the cold light of reason".

È difficile trovare nei suoi scritti un concetto che possa essere espresso in modo migliore.

The aspects of his personality described before and his deep professional commitment also made him a great teacher:[38] at least fifteen textbooks on geometry, topology, complex analysis[36] testify his didactic activity.