Hello,
1) If you limit the max-height of the image then you will get the white space before and next to the image, for example http://prntscr.com/oowj7k
If you just want to place the gallery slider at the top use the following code
.gallery_vertical .woocommerce-product-gallery {
align-items: flex-start;
}
2) To limit the zoom window use
.mfp-figure figure img {
max-height: calc(90vh - 50px) !important;
}
Regards