To make image changes to a product which is already live or accepted by Zalando, then this must be done through Partner Care.

If the product is in rejected, then it is possible to make changes to the images via the API connection that is setup in your ChannelUnity dashboard.

To make changes to images, please follow these guidelines set by Zalando via this link: https://partnerportal.zalando.com/partners/s/article/Updating-your-article-images