The X10 Mini and X10 Mini Pro do not have optical (hardware) zoom capability. So there is no zoom feature in the default camera application.
However, there are some camera apps that can digitally zoom the image. This is done through software and the image quality is reduced considerably (Its just like taking a small part of the image and stretching it).
Some of the camera apps in the market with digital zoom capability are,
Vignette
Camera 360
Camera ZOOM FX
But IMHO, digital zoom is not worth it. Its better to take a normal picture and then edit it using any image editor on a PC or MAC.