I don't think Zoe's main problem is in her **Trouble Bubble** or her **Paddle Star**. I think it's in **Spell Thief**.
As someone who enjoys playing Zoe a lot, I have no idea how this skill made it to the live servers and how it has survived for so long in its current form in the game.
- Virtually no cool down.
- Zero mana cost.
- Upon activation, not only do you get the effect of the spell/item active but you also get a free Ahri **Fox Fire** for added damage.
- You get movement speed.
- You can pick up several spells one after the other and use them with no cost, risk or punishment.
And those are only the direct effects. Depending on the situation it can also enable you to roam with a Ghost or just get back to lane faster. Your own Summoner Spells get trivialized, as you can simply pick someone else's spells. If the enemy has a bunch of items with actives, you suddenly get so much free stuff to use. Zhonya's, Youmu's movement speed, Redemption, etc.
Very often I find myself winning fights or getting out of sticky situations just because how free and how powerful this **W** is. I don't think it's right that a character infamous for her burst and great neutral objective control gets to use such an overloaded skill on top of everything else. Sometimes I use a spell when I'm diving an enemy or whatever and what grabs the kill in the end is one of the missiles from the not-Fox Fire part of the skill.
I enjoy Zoe a lot, but I don't think her **W** is in the right place.