Back display is a low-res jpeg preview. The preview is a single, small jpeg file that must be resized from it's full view form for any display size other than 100% zoom, which is why the zoomed and computer images look the same. This resizing will result in loss of resolution and the possible introduction of noise.
As Moab Man stated, what you are seeing here is called Moire, and it's induced by certain detailed patters, often found in clothing, and can pop up when the image is resampled within the camera. Marketing departments seem to like Moire more than post people, leading them to promote the removal of Anti-Aliasing filters, which eliminate this pattern in the actual photograph while simultaneously softening the image slightly, on many cameras.
Seriously though, if you are curious, take the image on your computer and repetitively resize it to 25% the current size. At some point you may just introduce the pattern again on the computer as you lose resolution.