I own a Zeno. If your son has one or two bumps at a time, it may be effective. I tried using it on large pimples, when they first come up. I think it probably did help them go away faster, but did not keep them from coming.
Have you seen dermatologist? For the price of the zeno, I would see the doctor. I have been prescribed Accutane twice, as a teen and after my son was born. It is a miracle drug for acne. It does have some side effects. The serious ones are very rare and the normal ones (dry skin, dry hair) are so worth it.
I also use a regimen thay I learned about on acne.org. But, I think for teen hormonal acne, accutane is the best way to get ahead of it. The acne.org regimen is a great maintenance system. I also know several teenagers who have used accutane lately, with great success.
Please get this under control ASAP. I don't think people who do not have acne quite understand the psychological and emotional effects it has on teenagers. I was lucky to have a parent who had acne as a teen. My dad was willing to do anything to help me. Thanks to quick and aggressive treatment, I was able to enjoy being a teen and am scar free.