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It is quite common for image zooming not to show on non-standard Magento themes. The fix is usually to modify the template, ensuring that the zoom JavaScript and CSS files are being referenced; that the template is fetching the correct size for large and small images and that there are no conflicts with other scripts in the template.
In all cases, ensure that product images you uploaded are sufficiently large to be zoomed. At least 500px width and preferably more than 800px width. The larger the image, the higher quality the zoom. Some small images may not zoom at all.
Also consider installing a Magento image zoom extension that already supports the RWD theme such as Magic Zoom Plus. Zoom extensions typically support many themes by default.