Is it safe to take a bar and a half and a 7.5mg hydrocodone?

Generally speaking the answer is no. Talking opiates with benzodiazepines leads to greater risk of upper-respitory failure. There are some instances where a doctor could prescribe both, but the dosages would be very specific.

From a recreational standpoint it doesnt make sense, the xanax would mask the euphoria that one derives from an opiate.