How does Zach benefit from this scenario? And from Chicago's standpoint, they'd necessarily have to be negotiating with Zach before the swap took place. Basically, this sign and trade scenario is a roundabout way of trading for his rights. They would simply cut out the middleman, so to speak, and in the process, have to give up a lot less to do that rather than the sign and trade scenario.
He goes to a contender that makes cap room for him from a team that otherwise might not have dropped cap space. For arguments sake lets say the Hawks consider Hossa or Hjalmarsson expendable if and only if they were to get Parise. They could wait until July 1st, try to sign Parise and then try to shop whomever to get under cap, but they might end up paying a lot more as other teams drive up the price.
Zach benefits because he is still going to get "roughly the salary he wants" but gets to go to a contending team and not settle for the Wild or Av's. Yes, Zach could do this anyway but maybe the Hawks don't even bother knowing they have more work to do, or maybe the Hawks sign someone else right away and then have no room for Parise.
All of this is based on the precondition that Zach doesn't want to play here for "roughly the salary he wants" for whatever reason, which I don't buy into. Also as you note; this would be more or less equivalent to trading his rights for conditions yes, but I don't think you can send players back on conditional trades.