I took Zyban twice years ago, no mood swings or anything although I did break out in hives both times. DH took Zyban & suffered mood swings, he also took Champix more recently & stopped as he found he suffered insomnia & nightmares on them. I have a history of depression & anxiety, DH not so much. I think it's just a case of how the individual reacts.
Both have reported side effects, I would be careful on either of them. Having said that, the Champix seem to work quite well, DH did quit & then was unfortunate enough to start again months later.

Good luck to your DH, it's tough but can be done