Hi Vijay,
I think either the package or the name of your logo start with Z but the other doesn't?
Z (or Y) is in the name range reserved for customers. The object cannot be assigned to a non-customer package, since it belongs to a different name range or namespace.
I would suggest you name your logo Z* and add it to a package which starts with Z also. So both objects would be in the customer name range.
Best regards,
Andreas