Btw, the absolute best case scenario, that I can figure, is the Knicks use some combination Vonleh/Dotson/Burke to entice a team to take on Courtney Lee.
Then win the lottery. Under normal circumstances, you definitely keep a potentially generational talent like Zion. But if the Knicks hear that Davis coming to NY means that any one of Kemba/Kyrie/Klay/Kevin (Durant) is willing to come play at MSG, in front of Celebrity Row and Breen&Clyde and all that good stuff, then you take a deep breath and move Zion because Zion < Davis + another all star. But you'd obviously want to be pretty confident in what you're hearing from the agents.
Anyhow, then you trade Zion/THJr/Lance/future picks for Davis. And you'd have enough cap space for a) Durant + MLE sized player + a mini-MLE exception or b) one of the other guys plus almost two MLE size players. And once you have Davis+Durant+Porzingis in NYC, then you get vets taking sweetheart deals at the end of their careers, like the Warriors get. You can then have a rotation that looks like this:
Rubio/Ntilikina/Durant/Davis/Porzingis
Mudiay/IsoZo/Knox/Taj Gibson/Mitch
(Presume Durant to a max contract, Rubio to ~$11 per contract, Mudiay to the mini-MLE on some sort of loyalty discount, and Taj signing for the vet min to come play in his hometown)
That's the best case scenario. It's good enough to win the East, possibly the title. It just requires a) a Courtly trade in the next week and b) all the luck in the world.