The Switzerland goalkeeper finished his first season with Inter as a Serie A title winner.
Zenga said at Milano Football Week: "I remember when (Andre) Onana arrived, many had doubts and then he did well, the same happened with Sommer.
"When he arrived, I was someone who at the beginning was not completely convinced, instead I was happy to be proven wrong. It is right to face your own opinions. What he has done this year has been of the highest level, also because the team has grown a lot.
"Football changes, but what doesn't change is that if you have a good goalkeeper, a good central defender, a good midfielder and a striker who scores goals in the end you win. Inter changed the goalkeeper, they changed Skriniar, Brozovic, Dzeko, Lukaku... this was the skill.
"In my opinion we have returned a bit to the 90s: one year Inter won, then Sampdoria, then Napoli, then Verona... In the last 3 years we have had three different winners."