Check if GUID is empty (in C)

I want to check if a GUID structure is empty/all fields are 0. This is the code I wrote:

#include <windows.h>

static BOOL IsEmptyGuid(const GUID * const pGuid)
{
    return \
    (pGuid->Data1 == 0) &&
    (pGuid->Data2 == 0) &&
    (pGuid->Data3 == 0) &&
#ifdef _WIN64
    (*(DWORD64 *)pGuid->Data4 == 0);
#else
    (*(DWORD *)pGuid->Data4 == 0) && (*(DWORD *)(pGuid->Data4 + 4) == 0);
#endif
}

/* GUID definition from MSDN
typedef struct _GUID {
    DWORD Data1;
    WORD  Data2;
    WORD  Data3;
    BYTE  Data4[8];
} GUID;
*/


int main() {
    GUID guid1;
    guid1.Data1 = 0;
    guid1.Data2 = 0;
    guid1.Data3 = 0;
    memset(guid1.Data4, 0x0, 8);

    printf("Result: %u\n", IsEmptyGuid(&guid1));
}

A safer way to check if field Data4 equals 0 is to iterate over every byte and check for it's value. But, I find the code from above more expressive.

I would like to know, is it correct? Is it safe?

Thank you!