Oh man, you have my sympathy for having to kick both benzos and opiates at the same time... my advice is to do one, then the other. I'd kick opiates first as it will take much less time and you can continue using the benzos which will help somewhat (not a whole lot) with the opiate w/d symptoms. Then once you're stable and clear of opiates, you can start a slow taper on the benzos. Reduce by 10% every week or 2 weeks. Drop 10% of your dose, wait until you feel normal, drop another 10%, etc. By the end the drops will be tiny but that's because if you're on, say, 2mg of clonzapem (just making something up), dropping 10% is down to 1.8mg. But if you're at 0.5mg, if you dropped 0.2mg, you'd be nearly cutting your dose in half and would experience significant withdrawal.
All of the literature support this sort of slow taper. You can get off benzos without dangerous or terrible withdrawal, but it takes time and dedication and NEVER cheating on the dose.