Zyban is an atypical antidepressant. In your shoes I'd throw out the pills and stick to the meditation. While anti-depressants are claimed to not be addictive physically by the medical community, those that have taken them (like myself) can tell you a whole other story about emotional addiction to anti-d's, and the terrible "crash" they had to overcome in order to kick them.
Nicotine is an heavy weight in the addiction department...helluva thing to give up, so I can understand anyone's need to find support in another drug. At the end of the day however I don't relish the thought of trading one habit for another. Careful with the Zyban, it could turn out to be a devil in disguise. Using meditation is an wonderful way to help when the "crave wave hits"....as well as any form of exercise, hobby...anything, as long as the hands & mind are kept busy.
Kudos on your quit!!!....I'm 3 years clean now and finally able to call myself a non-smoker instead of a struggling quitter

Hang in!