volume user full but plenty of iPhone/iCloud storage available

See this Apple support document regarding dealing with zip files. Create or open ZIP files on your iPhone or iPad - Apple Support

Cloud storage would have nothing to do with this unless you are using iCloud Drive. Do you know how large the files are in the zip file? That could make it that it could not uncompress the zip file. That could lead to the error. I see you currently show ample space on the phone. Are you trying to download to the Files app?

I've not encountered that error in the past, so I'm not sure about it, especially calling something User. Maybe someone with more info would be aware. How did you receive the file? Was it in an email or message?

ayorayj wrote: … I am trying to download in the files app so I can save them to my photos.

Can you explain what you mean by this? Downloading the files app doesn't make sense to me. What exactly are you downloading from and to?

What are you really wanting to do?

If you want to move pictures from the Files app to the Photos app, then in Files you use the More menu (•••) and choose Select, choose the pictures, then choose Share>Save nn Items. Is that what you're trying to do? After you're sure the pictures are in Photos, you can delete them from Files.

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