The Nordic forward, who a week ago was discharged from Covid-19, scored his double at 12 and 16 minutes of the first half. In Inter the Belgian Romelu Lukaku discounted, at 28m of the same stage.
Martínez, who was with the Argentine national team and scored against Bolivia, completed the entire match with Inter but without standing out.
With this victory, Milan continues at the top of Serie A, with 12 points, while Inter has 7 units.
For his part, the current champion, Juventus, with Paulo Dybala without leaving the substitute bench, he drew 1 to 1 as a visitor with Crotone, in which he started Lisandro Magallán (admonished).
Simy, from a penalty, opened the account for the premises and Álvaro Morata tied for Juve, who suffered the expulsion of Federico Chiesa.
Other results: Napoli 4-Atalanta (José Luis Palomino, Cristian Romero and Alejandro Gómez) 1; Sampdoria 3-Lazio (Joaquín Correa) 0.
The program for Sunday:
. A las 7.30: Bologna-Sassuolo.
. A las 10: Spezia-Fiorentina and Turin-Cagliari.
. At 13: Udinese-Parma.
. A las 3.45 pm: Rome-Benevento.
. At 3:45 pm: Verona-Genoa.
Positions: Milan 12 puntos; Atalanta 9; Juventus y Napoli 8 (x); Sassuolo and Inter 7; Sampdoria, Verona and Benevento 6; Rome and Lazio 4; Genoa, Bologna, Fiorentina, Spezia and Parma 3; Cagliari and Crotone 1; Turin y Udinese 0.
(X) A point was deducted for not showing up to play against Juventus.