Zend Script Decoding

I have a problem with a large PHP script that I legally own however it's encrypted with the Zend Optimizer. It was registered in the name of a domain that I no longer control, but I'm the registered owner of the script. The vendor doesn't answer my emails. I need this script decoded so that I can continue to use the script. No generic responses please. Only bid if you absolutely know how to get 100% of the source code back.