Size down zoomed product images to fit browser height

This customization will make the image fit on shorter screens when the zoom pop-up is used.

Example before:

Example after:

Allowing the customer to see the whole product without scrolling. 

Code:

/* -- code to make zoomed images fit browser height -- */
.mfp-container img{max-width: 90vh;}
/* - end - */

Where do I add the code?

Use this link to learn where exactly to add this code snippet:

Where to add your CSS style code