Zoom-in for product images is available by default. The zoom-in is visible when a customer hovers on the product image.
However, the zoom-in quality will depend on the original resolution of the product that you upload on the product. If you upload a low resolution image say lower than 500 pixels, the zoom-in quality will be lower. Although if you upload a product of higher resolution, say greater than 1024 pixels, then the image zoom-in will be optimum.