Iframe Content image Scraping

Describe the problem.
I cannot find resources that make the explanation clear enough regarding the scraping of image content within an iframe. I am trying to capture the main, fullsize image shown in the zoom window (div.main-img-wrapper)

Url: https://buy.gazelle.com/collections/iphones/products/iphone-xr-64gb-at-t-1

Sitemap:
{"_id":"gazelleinv","startUrl":["https://buy.gazelle.com/"],"selectors":[{"id":"Category_Link","type":"SelectorLink","parentSelectors":["_root"],"selector":".site-nav__submenu a","multiple":true,"delay":0},{"id":"Product_links","type":"SelectorLink","parentSelectors":["Category_Link"],"selector":"a.yc-product-item-link","multiple":true,"delay":0},{"id":"Name","type":"SelectorText","parentSelectors":["Product_links"],"selector":".product-title h1","multiple":false,"regex":"","delay":0},{"id":"Cost","type":"SelectorText","parentSelectors":["Product_links"],"selector":"span.discounted-subtotal","multiple":false,"regex":"","delay":0},{"id":"Color","type":"SelectorText","parentSelectors":["Product_links"],"selector":".swatch label > span","multiple":true,"regex":"","delay":0},{"id":"Price","type":"SelectorText","parentSelectors":["Product_links"],"selector":"form > div[data-price-wrapper] span[data-product-price]","multiple":false,"regex":"","delay":0},{"id":"Image","type":"SelectorElementAttribute","parentSelectors":["Product_links"],"selector":"div.main-img-wrapper","multiple":false,"extractAttribute":"src","delay":0}]}

There are no iframes here. You can get the zoom img URLs just by using Element attribute, e.g.

{"_id":"forum-gazelle-images","startUrl":["https://buy.gazelle.com/collections/iphones/products/iphone-xr-64gb-at-t-1"],"selectors":[{"id":"Product","type":"SelectorText","parentSelectors":["_root"],"selector":".product-title h1","multiple":false,"regex":"","delay":0},{"id":"Zoom images","type":"SelectorElementAttribute","parentSelectors":["_root"],"selector":"div.slick-track a[data-zoom-image]","multiple":true,"extractAttribute":"data-zoom-image","delay":0}]}