Hi,
1.) You’ll need a plugin with zoom functionality.
2.) You’ll have to change the max upload size if the images you’re uploading is larger than your site’s upload limit. You can do this with a plugin or by editing your site’s php.ini file or by adding snippet like this on your functions.php.
@ini_set( 'upload_max_size' , '64M' );
@ini_set( 'post_max_size', '64M');
@ini_set( 'max_execution_time', '300' );
Note: Loading of large images isn’t recommended if you’re concerned with the page’s performance.