Quote from a news article about it:
I've read through the FAQ and feel it will be interesting to see how these "zeutered" dogs grow. It does lower the testosterone level by 41-52% and is only approved for 3-10 month old puppies, so I'm wondering how it affects growth compared to surgical neutering or leaving the dog entire.The newest in dog sterilization, Zeutering, is an FDA approved, non-surgical way to “neuter” your male dog, without the use of anesthesia, while leaving the testicles intact.
The chemical neutering process involves sedating your dog to calm him and injecting a solution of zinc-gluconate, L-Arginine, and water into each of the dog’s testicles. The dog is then marked with a small tattoo to indicate that he’s been neutered, and one month later, he is completely sterile. The process greatly reduces the costs of neutering and the time it takes to perform an operation.
There is little to no recovery time, no swelling, no irritation, no stitches.
The injection, made by Ark Sciences, called Esterilsol, is FDA approved for use on puppies between 3 and 10 months old. About 300 puppies have been zeutered to date, and the long-term effects of the procedure are still being researched.
(Source)
It is also estimated to cost 1/5 as much as traditional surgical neutering.