Will zithromax help me if my bronchitis is viral and not bactirial?

Highly unlikely that Zithromax will help with a viral infection as it is an antibacterial (unless you have a bacterial infection secondary to your viral infection).

Zithromax is an macrolide antibiotic related to erythromycin. It fights bacteria in the body.

Zithromax is used to treat many different types of infections caused by bacteria, such as respiratory infections, skin infections, ear infections, and sexually transmitted diseases.

In children, it is used to treat middle ear infection, pneumonia, tonsillitis, and strep throat.

http://www.drugs.com/zithromax.html