Don't mistake 'well curved' for 'good'. Zoo and also Maverick have many ways to deal with CB top. Firstly, it's speed. Because both deck can put pressure on the board before CounterTop is established, CounterTop is too slow and janky. Also,
Green Sun's Zenith gives them an out to escape the curve. GSZ with X=2 or 3 depending on how much spare mana he has can easily net a
Qasali Pridemage if he needs one. I'm not a fan of
Counterbalance versus fast aggro decks if you do not have a way to reset the board, like
Wrath of God or
Pernicious Deed.
Also, when dealing with green based aggro: do not underestimate the power of
Gilded Drake +
Submerge. It leads to awesome plays like
Submerge in response to fetching or
Knight of the Reliquary activation; or just steal the Knight with Drake and then get back the Drake with Submerge and steal another Knight.
I prefer that method if you don't run
Punishing Fire and are hesitant to run
Vedalken Shackles because they side in artifact/enchantment hate against you anyway.