There are (2) kinds of zoom with a camera: Digital and Optical. When you look at the specs of a camera you will frequently see something like "4x optical, 32x digital". What this means in laymans terms is that the actual camera lens glass 'zooms' at 4x. Then, when you zoom PAST 4x, the digital 'zoom' kicks in. When the digital zoom kicks in, the images is actually no more clear than if you had zoomed at only 4x, as the digital zoom is actually just taking a piece of the 4x image and 'enlarging' it to take up the whole screen.
What this means for you is: to get better images of small objects, you need better optical zoom. You can use a cell phone camera and a loupe (less than $10 on amazon) to get great images of mintmarks and dates. It takes a steady hand using this approach, but it's cheap and it works. The flat bed scanner is a nice alternative, assuming you have one.