Mavericks trade THJ and two 2nd-rounderd for DFS. He just fits on the Mavs so well and I think they'd jump at the opportunity to get him back.
Magic get THJ to drastically improve their shooting. Not enough people are acknowledging just how good Tim has been as a 6th man this season and Fultz, who the Magic are trading away here, has played only 5 games and is not considered a great shooter.
The Nets get a young playmaking point guard. They have a lot of shooters so Markelle fits very well. He is a good defender too, so he could form a very good teo-way lineup with Bridges, Johnson, O'Neale and Claxxton. The Nets reportedly want a lot for DFS, but Markelle is a potential PG of the future they need and they get some 2nds to sweeten the pot.