Hey, I am using the LimeSurvey Cloud,
What is the URL where the zip with all resources is stored (resources from the responses, like images from users)? It should be a URL that ends with the name of the file: .../resources-survey-<id>.zip.
Inside the settings I can hit "export" and the zip will download from a URL link like this: https://<cloudHostName>.limesurvey.net/admin/export/sa/resources/export/survey/surveyid/<id> but that's not where the zip is stored, it's just a redirect. 

I want to download the ZIP file using a program. Unfortunately, the API does not yet have a function to download the resources. So that's why I want to download it from the URL in a browser.

Not using this a lot, but my guess would be that you'll find it in /uploads/ and there should be a folder for each survey. There is a good chance that this ZIP file won't be saved there, but created on the spot and you will only find the original files there. But have a look.

How does the rest of the URL look like?
limesurvey.net/admin/uploads/.../resources.zip ?

As @holch already mentioned these files are stored in the "files" folder of the survey.
"upload/surveys/123321/files"

Here the files are stored with the tmp filename of the upload.
 

To get it, export the responses, have a look at the upload column where you get the original name and extension and the tmp name.
So you may merge them, rename and download.

Joffm