The camera was dropped on the lens and zoom won't retract

Try this first, power off and gently push the lens barrel sideways - not back in!, If the barrel and the lens move slightly, you will get it working after some more manipulation in the same way. If it does not budge, sorry to mention this but your camera sustained more damage and you cannot do do much on your own.

not sure if this link will help you out..
Lens won retract Google Search

Hi,
Unfortunately that isn't repairable. The most likely reason as to why the lens won't retract is because the water fried its circuit board and that is a costly repair.

The lens has probably got something in the retraction mechanism that is stopping it retracting. This can be something as simple as sand or grit or as a result of a drop or knock. In most cases the camera will need to be stripped apart to remove the lens assy before it can be repaired. This is best left to a professional camera repair shop.

i think you should take the battery out then hold the power button for ten seconds then put the fully charged battery back in if it doesnt work go back to the store and have them look it over.,

We had this problem for about 2 weeks, we discovered that having the camera auto retracted after the "ZOOM ERROR" message, giving the camera couples of light slaps (slap the camera's LCD side and aim the camera down), this fixed the camera right away

I did the same thing to my camera (twice) and I just took it back to the place where I got it. Since it was within the 6 month return period- they let me exchange it for no charge.
They told me that when the camera hits something while the lens is out, it knocks the lens out of its groove, which is why you can't get it to retract.

The suggests the zoom control failure
Only Olympus can fix it to it will have to go back.

I banged mine around several times and tried to force the retractable lens in and out. Neither of these things worked. I finally thought "what the heck it's broken anyway" and used a bobby pin to try to force the outer lens cover off. After applying just slight pressure it unjambed the lens cover and it works fine now.

I posted the same problem on the 15th June and in the meantime I have been playing around with the camera. After holding the camera upside down and gently tapping the back of it, the lens decided to work and retract back into the camera. Not the most technical advice I know but it seemed to work.