What does “a build” mean for you?
There are a number of intermediate files that you don’t have to include in an installer or download, no matter whether you ship a zip file or an actual installer. Make sure to exclude all of those (using whatever method you prefer – anything from installer maker scripts to .gitignore) and your built engine/editor will be the smallest necessary size.
That being said – once the artist runs the editor, and it builds/bakes/processes all the art, the actual disk usage will be quite big for artists, too. That’s just what it is to use Unreal Engine. If you need all the fancy bits of this engine, you have to live with the size explosion, because that’s what’s needed to deliver those.