How to open a .zip file which is embedded in .xlsx file?

I have a .zip file which has been embedded in a .xlsx file (excel ). But everytime I double click on the file it keeps giving this message:

Cannot start source application for this object. There may not be enough space in memory.

How can I open the .zip file? I have downloaded the unarchiver and also OpenXMLConvertor.But I dont know how to use them to extract the file.

I have Microsoft Excel 2011 (Version 14.0.0) and MAC OS X mountain lion, 64 bit , macbook air (2013). Kindly help