Many digital cameras come with claims that they have a "digital zoom" in addition to, or instead of, optical zoom. If you have such a digital camera, do yourself a favor right now and get your camera’s manual and find out how to disable this feature. You’ll be much better off without it.
All a digital zoom does is show you fewer pixels from your picture. This apparent zooming acts nothing like a normal optical zoom, and in fact it will reduce the quality of your pictures enormously.
You can get the same, or perhaps better, results if you take the picture without digital zoom and then crop it later on your computer. So turn it off!