Hello,
To enable zoom on mobile, you need to copy product-image.php file from legenda/woocommerce/single-product folder into child theme with the same folder structure and make changes according to screenshots http://prntscr.com/j5v7eu > https://prnt.sc/j5v7le
+ remove this http://prntscr.com/j5v9bn in legenda/js/etheme.js > http://prntscr.com/j5v9t9
The etheme.js file can be changed only via parent theme, so after each theme update, you need to repeat changes there.
Regards