The former Bologna striker is wanted back in Serie A by Roma this month.
But after Zirkzee created his goal against Leeds on Sunday, Cunha said: "Josh is a pleasure.
"I feel like he has a lot of quality. Of course, his situation is not easy, but he has everything to change the situation. We need him. He needs to understand this and then everyone can count on him.
"But yeah, we are here to push him. And I think after the goal last week and the assist today, I think it will give him confidence to be more with us and then understand more his role in the team."