sorry Guys you can't fix the zoom problem
I work at a tv station and I have the luxury of having 10 eng
I had them take a look at it, and they told me that the way that the zoom mechanism was made, the wire tape will eventually crack,(very small hair line crack) results ... no zoom or every now and then it will touch and zoom on its own.... sorry to bring the bad news the only way to fix it is to go through canon.

if it has not happen be ready

I visited Canon here in UK. "Have you had reports of this?" "No" . . . ok . . here we go . ..

G

I had the exact same problem, and i had to take it to canon, luckly they were right down the street