While I am in the party that thinks Speed is way over-stating the impact that missing Zach has had on the team, I think a lot of people are combining two different issues here.
Zach, if anything, was a very high IQ player, with surprisingly quick feet and hands. Did he make rookie level mistakes? Yeah (but I suspect some of that is reputation based. I.e., he's young, unknown and a big goofy white kid). But the guy also made a lot of quick decision blocks and smart choices that were really lacking on this years team.
But at the same time, he's missed basically the last 2 seasons. So it's understandable why people are a little leery of supporting him, etc., especially considering the absolute waste of a career that Meyers Lemon had.
I think Zach, assuming he has his injury issues behind him, definitely has a role on the team. Could be a starter, could be a the backup PF/C (I'd take his defense with his offensive skills over Kanters offensive skills and lack of defense awareness/effort).
He's not a slow, plodding player. I just hope his injury issues are a thing of the past.
I'd rather have Dame, Powell, Roco, (healthy) Collins and Nurk as the starting 5 next year, with a backup PG, Ant, Little/Jones and Kanter as the backup C.
Hopefully the backup PG is who they trade CJ for (+ picks...hey, a guy can dream).