.product-simple-image .simple-image-desk {
  display: none;
}

.product-simple-image .simple-image-mob {
  display: block;
}

@media screen and (min-width: 750px) {
  .product-simple-image .simple-image-desk {
    display: block;
  }

  .product-simple-image .simple-image-mob {
    display: none;
  }
}