No...Zeus is its own thing, AFAIK, though I guess it's described (by the Zeus maintainer) as "like Zeus but in pure Ruby, totally automatic, alpha and limited compatibility"
https://github.com/burke/zeus#related-gems
I started using Zeus a couple of weeks ago and then switched over to Spring last week...I never figured out how to get the custom Zeus files to let me run regular rails/rake commands with certain flags and parameters, but Spring pretty much worked right out of the box. It works so well that I've been wary that it might cause issues in edge cases of test configuration, but haven't run into any yet...and now that it's a part of Rails, guess I'll be even less wary.
It's definitely changed how I do TDD for Rails, in that I will actually do TDD for Rails, because the tests run so quickly. Yes, being hindered by Rails bootup just to run tests might be indicative of unneeded coupling, but sometimes a project doesn't require great abstraction, but still needs decent integration coverage. Spring is pretty handy for that.