But still, there's the fact that Florida was willing to move him. Prospects that get traded do not have a good track record - the team that has them is following them closer than teams that don't. Every so often a Filip Forsberg thing happens where a team just misses on a guy they had, but if you look at the track record of guys that Tampa traded versus guys they kept, for example, it doesn't look great.
That said, that's the kind of return I'd expect for Zacha. Bennett plays a more physical game and he'd had a big playoffs for Calgary, I've still never really seen a player's game change that much that quickly after being dealt. He went from being a 3rd/4th liner to immediately being one of the top goal scorers in the NHL.