Even if a little bit more complicated it's possible to arrive at Nexa Center going through the Politecnico Main Entrance (corso Duca degli Abruzzi 24). In this case follow these instructions that let you go through Politecnico Campus from east to west.

pass over the first court (after the main entrance)
get into the building passing one of the sliding doors (left or right is the same thing)
follow the indications (red signs) to “departments” (going along the Aula Magna) until arrive the the internal court
pass the internal court
get into the entrance hall of the Departments Building and overpass in order to reach Corso Castelfidardo
turn on the right, reach the red light and cross the avenue
turn again on the right following the fence and get into the green gateway
go straight ahead going along leaving at your right the dining hall,“T” Aulas (Cinema Engineering), Boella Institute and “I” Aulas until you will arrive at the parking.