Looks sweet! Zombie tribal is so close to being amazing, and adding
Collected company is a clever idea. The major downside seems to be
weakness to sweepers like
Anger of the Gods or
Supreme Verdict.
Collected Company dances around that pretty nicely since it's instant speed, but maybe something like
Lord of the Undead would be good to get back your
dead zombies?
Sideboard looks pretty good and it's pretty clear you realize your tough matchups will be control, so being prepared for that is smart.
Dash Hopes is interesting as an interaction card, though I imagine you're tapping out pretty much every turn so it may not fir too well.
I think as long as you can play around sweepers, you're going to find the deck extremely powerful. Good luck!