Both players have been linked with January departures to Italy, where Napoli are keen on Mainoo and Roma want Zirkzee.
But Amorim said ahead of today's trip to Liverpool: "I understand that but they are our players and we need everyone to have a good season.
"I also know that in our club everything is a lot of noise. Players are not playing. They want to play, and there's a World Cup. There are agents that listen to the players, talking all the time."
Mainoo has made five appearances from the bench in the Premier League so far. Zirkzee, meanwhile, has managed just 82 minutes across all competitions this season.