This has nothing to do with Qt. Qt is not a compiler or linker.

You cannot use raw C++ objects in DLLs unless your compiler matches the compiler used to create the original DLL.
You can use C functions and structures in foreign DLLs.
You can use objects defined in ActiveX DLLs using generic Windows programming or Active Qt.

Given that WinUSB follows the usual Windows API conventions this task should be no more difficult than including the relevant header file and linking the relevant library.