Are there any words besides ones that don't have start with an s followed by a consanant (uno studente, uno studio) or a z (uno zio, una zia) that would start with uno instead of un?
No, there aren't.
And is this correct
Un Libro (Plural): Due Libri
Una Penna (Plural): Due Penne
Uno Studente (Plural): Due Studenti
Yes, perfect.
Getting the grasp between the singular and plural.