Gold MemberUsername: Project6
Post Number: 3356
You have dust on your sensor. The only way to clean this is to lock up the mirror and use a bower on the surface of the sensor. Do not use any type of canned compressed air and do not let any thing touch the surface of the sensor.
The clue is in the zooming and it would probably be more prominent at the smallest aperture.
If the camera is still under warranty, send it in for a professional cleaning. The cleaning procedure is intimidating to some aso if you are not comfortable with it, send it in.