I've updated the API to allow underscores like it should.
Deletes are a little more challenging, I think the only good way to do that would be to provide a method that'd return the entire contents of the zone with an index so you could call delete on the index and I was reluctant to commit that much time to this project.
Thanks for fixing the _ issue.
I have created a PR against lego for formal inclusion
Deleting would be nice - but is not required.