I used to mix them all the time. Coke (snort, smoke, and shoot) and meth would make me instantly paranoid by the end of my career with them. So I'd only do them with benzos. I recall that hospitals will give you iv benzos when you come in freaking out on coke so in principle I don't think there's any majorly dangerous interaction (at least in most individuals). For me, though, it would eliminate the one protective mechanism I had when on them: paranoia, which kept me from going outside and doing nutty shit and getting arrested. For coming down, it was great. But I would take benzos to get high without paranoia, then do insane shit cuz I was cracked out but had no fear, and end up in jails and hospitals a lot. Also led to insanely high doses of coke and benzos (say 20-40 mg of clonazepam or alprazolam til that got too expensive & I switched to phenazepam; at one point I was taking upwards of 1g-2gs of phenaze daily -- yes grams -- clearly it was always very very heavily cut toward the end, so I'm guessing really closer to a couple hundred mgs at most; probly would've died if I ever did get a 97-99% pure batch as advertised).