Make an image zoom out to a larger, different image

I have a set of wide images, about 1330 pixels wide by from 250px to 600px high.
I want to display on my website about 500px wide of the image (i.e. a cropped part of it, so that the user can see clearly what it is, rather than it being a shrunk down version of the whole image), and for the user to be able to click on the image, so that it zooms out to the full image at full size.
I know I can use the Transform function in CSS to enlarge an image, but I don't know how to change from the first image to the second image. I am fairly competent in HTML and CSS (and the Transform function), so I just need the basic code, which I imagine is a five minute job for somebody who already knows how to do it!

I also want a mobile phone user to be able to scroll the image left and right on their screen - because the images are too wide to display on a mobile phone, I want them to appear in some sort of box, which allows the user to push the image left and right to view more of it. I know how to use @media and max-width, if that helps.