The Leafs need to move out some contracts asap if they are going to get involved in the NCAA FA market and sign their own ELC's - at 49/50 rn
A Mrázek move could could get do that, but I'm not sure you clear a spot in a Duszak or Menell trade because teams might not even do a 7th there. They'd likely want to exchange for a different signed player.
I also do not hate just moving Holl now (probably for a 2nd) and adding a new #8 at a similar cost to Hagg to FLA. He's quite possibly out of the Playoff picture now:
Gio-Brodie
Rielly-Lyubushkin
Muzzin-Holl/Liljegren/Sandin