Sorry, I see now. Thanks for advise.
“full” can be changed on “large”, “medium”
I solved this problem in this way
/wp-content/plugins/yith-woocommerce-zoom-magnifier/templates/single-product/product-image-magnifier.php
find the string
list( $magnifier_url, $magnifier_width, $magnifier_height ) = wp_get_attachment_image_src ( get_post_thumbnail_id (), "shop_magnifier" );
after that add
$dfsefwf = image_downsize( get_post_thumbnail_id (), "full" );
$magnifier_url = $dfsefwf[0] ;
Exactly the same problem. The problem is not solved as I see
