Sorry, dumb question. Are you saying that abrupt withdrawal from the combination of those (addicted to both) can cause those symptoms and death, or either one alone can do that?
I still remember the wonderful feelings that prescription oxazepam (benzodiazepine) gave me over 30 years ago and have no doubt a person could get addicted in a hurry. Think I had ten tablets total.
Either one alone. You can in fact substitute one for the other , and in fact alcohol detox usually uses a benzo to wean you off, slowly decreasing the dose.