I don't call it "brain zaps." I call it "brain buzz." I c/t'd off Valium 74 days ago and it hit me (along with d/p and d/r) on Day 16, about the time the Valium in my system got pretty low. The d/p and d/r finally went away at about Day 46 or 47, but as I sit here writing I can feel the brain buzz just flowing from my brain.
I had "brain zaps" at first, little popping sounds in my brain, but they didn't last long. The "brain buzz" is 24 hours a day, 7 days a week. I've asked people who've been off longer than me if they've had this and most of them seem to. The average time that it seems to begin to fade is about 4 to 6 months off. Mine isn't as intense or as annoying as it was the first six weeks or so, but it's there nonetheless. It keeps me awake at night, just buzzing away. It's there all the time, with the exception of when I'm washing my hair in the shower and, on occasion, if I really get into a good TV show or movie.
I hate to tell you this, but it's probably just going to buzz and buzz and buzz even after you come off the Valium. If my "brain buzz" would go away I would only have relatively minor symptoms left. But as long as it's here, I'm dealing with constant low-grade anxiety and chronic insomnia, both caused by the "brain buzz."
I'm sorry I don't have better news, other than the fact that it DOES (I hope!) eventually pass.