Both are average players if you ask me, Hojlund has played almost 100 matches and hasn't yet scored up to 30 goals and Zirkzee has played almost 50 matches with less than 10 goals to his name for the club. Both of them combined has played almost 150 matches and scored not up to 40 goals, that's a very poor statistics. As for Mount, I don't even know the problem of Amorim, Mount should be dashed out for free.
Is there anything like dashing out of player, I don’t think so unless their contract as expired as a player and they go on free transfer to a new club. Mount may not have been the best of players since he joined Manchester United, but we should know that Manchester United are in the recovery stage and have not been performing well for a long time. All players are to be given some chance again and not disregard some players with such statements that they should be dashed out.
Man United is not in a position to dash out players for free as they really need fresh funds, and whatever the value, it means a lot for them. The players you mentioned earlier were bought by Man United at a high price, so it would be stupid to let them go for free, because for Man United, football is a business, so if they do that, it could be considered a failed investment.
So there are 2 options: still give them a chance with the hope of becoming better than before, or offload them at a cheaper price.