Pincushion, Barrel Distortion
The Z-120 shows signs of distortion at both the wide and telephoto end of the lens. The distortion is more pronounced at the wide end (left image), which is typical of many compact digital cameras, with less distortion at the telephoto end. In real world images the distortion shouldn't be much of a problem, unless you are photographing something with straight lines.
Another issue seen with some compact lens designs is a noticeable softness in one or more corners of the lens. There is going to be some loss of sharpness in most any lens as you move out from the center, due to different variables such as Depth of Field and the type of glass used in the lens. But how much and how the softness looks can vary with different lenses. With the Z-120 at the telephoto end, softness is most visible in the top left corner and a bit of softness in the top right as well. At the wide end of the zoom range, there appears to be a bit of softness in the lower left corner, but not in any other corner. The most pronounced softness is at the telephoto end, in the top left corner. The good news is it seems to be fairly high in the corner, as you can see from comparing the full size image (above left) with the cropped image. The word "camera" and the smaller text directly below it look blurred, but gets progressively sharper as you move into the image. In most real world photos this probably won't be much of an issue.
The following images were shot using manual exposure and manual focus under constant lighting. The 100% crops below are from the highlighted area. Noise at ISO 50 is very minimal, with a bit more showing up at ISO 100. The noise starts to become more prominent at ISO 200 and is very noticeable at ISO 400, though not entirely objectionable. The bigger problem I found is the loss of sharpness and detail at higher ISOs, starting with ISO 200 and getting much worse at ISO 400. The text and edges of the buttons are sharp and clear at ISO 50 and still pretty good at ISO 100, but start to get soft at ISO 200. At ISO 400, the image almost looks out of focus, and at first I thought that might have been the case. So I conducted this test twice, the second time using manual focus to be sure the focus point didn't change between shots, and came up with the same results. There could be some noise reduction being done at high ISO settings which is partially to blame for the loss of detail, though I am not positive of that.