Want to create a gradle script creating a package build of multiple projects

I have multiple separate projects with their own build script, and they are not added as modules to one root project. I want to create a package of all these projects and so that I can forward the package as a zip file to the other app teams to use our library. I want to execute the tasks that I have declared in other projects from one project. Is it possible to do it this way or I should have all the projects as modules in one root project to create a package.