Why is my full page zoom image pixelated / blurred?
Full Page Zoom displays your product images in full-screen so if you have small or low resolution images they may blur.
Shopify suggests uploading high resolution images, equal to or above 2048px by 2048px in size, please check the related documentation at https://help.shopify.com/manual/products/product-variant-images#image-sizes.
By choosing an appropriate size for your images, Full Page Zoom won't blur them when zoomed on most screen sizes.
If for whatever reason, you don't have high resolution images, there is an option to display the zoomed image in its original size to prevent the blur effect (Overlay preferences):