My downloads are not signed. It will take a number of downloads for SmartScreen to trust the download and the files contained in the ZIP file. There is no reason to be alarmed by this. This SmartScreen warning will reappear each time I update the software.
Simply click ‘More info’, the ‘Run anyway’ button will appear. Click that.
Same may happen in your webbrowser. It may warn about an unknown or not very commonly downloaded file. This is due to the fact that after each update the file is new.