The Chelsea loanees are set to meet their parent club in the EFL Cup on Wednesday night, as Frank Lampard is set to Stamford Bridge.
Mount, who was called up to the England squad in October, is hoping to overcome a foot injury to feature.
Former 'Blues' legend Zola has praised the club for letting the duo play, insisting that it is essential that they play regular first-team football.
"It's not only that [Lampard being Derby boss]," Zola told 'Sky Sports'.
"We believe that by playing against us is an opportunity for them to grow up quicker. The more they play against Premier League teams, the more experience they get.
"And we can make better evaluations on them. It was a great opportunity to see them play in front of us and we took the opportunity.
"There will also be a psychological component. They will have to play in front of a big crowd, the crowd of the team they belong to. It will give them a good test."
If either Mount or Tomori are to score, Zola does not know why they should not celebrate.
"It's down to them but why not? Hopefully they won't celebrate too much," he added