Nobody can tell you anything without proper system info or other technical details like the exact specs of the image file, your comp settings, how you "zoom" and so on. Throwing around vague terms is in no way useful.
The image is 27648 × 14848. When I use my mouse wheel to zoom the resolution is great. When I scale the image the resolution is awful.
When you say scale the image, do you mean the view in the composition window or do you mean the scale property in the layer's transform controls?
Screenshots would really help here.