Is it possible to change the image the Merchandizing zones use through code?

Yes. It uses its own template.

Just for sample

<% var item_image_url = item.cms.image.url.search('no_image_available.gif') === -1 ? item.cms.image.url : '/SSP Applications/NetSuite Inc. - CMS/CMS/Site-2/Published/Templates/no_image_available.gif'; %>

Thanks for your responses, but it seems that the CMS Merchzones do not use the merchandizing templates or JS files and use the CCT-View, or so it seems in 2020.1