I used ZRT Labs several years ago to test reproductive hormones and 4 cortisols. I thought they did a good job. However, when I went to my DO last year for the first time, and I took my test results from ZRT, she would not even look at them. She said they are not good and that their results are not accurate. But, when the DO tested all my hormones, the results were about the same - everything was low, low, low, just like with ZRT. So, that's all I know. Wish I could help more.
I am definitely interested in checking out testing for neurotransmitters.