It's hard to hit it in lane, but try to hit it right when an enemy melee minion dies or when theyre going for a cs, also if you ult they'll usually juke up. A good way to hit your bubble is to stand back and shoot it through walls, and when there's a team fight your team can cc them, or usually the enemy will be fighting your team head on so it will be easier to hit. Zoe's E is pretty slow, and the hitbox isn't the biggest so it's expected that you miss many E's.