NtQueryDirectoryFileEx - NtDoc

Native API online documentation, based on the System Informer (formerly Process Hacker) phnt headers
#ifndef _NTIOAPI_H
#if (PHNT_VERSION >= PHNT_REDSTONE3)

NTSYSCALLAPI
NTSTATUS
NTAPI
NtQueryDirectoryFileEx(
    _In_ HANDLE FileHandle,
    _In_opt_ HANDLE Event,
    _In_opt_ PIO_APC_ROUTINE ApcRoutine,
    _In_opt_ PVOID ApcContext,
    _Out_ PIO_STATUS_BLOCK IoStatusBlock,
    _Out_writes_bytes_(Length) PVOID FileInformation,
    _In_ ULONG Length,
    _In_ FILE_INFORMATION_CLASS FileInformationClass,
    _In_ ULONG QueryFlags,
    _In_opt_ PUNICODE_STRING FileName
    );

#endif
#endif

View code on GitHub
#ifndef _NTZWAPI_H

NTSYSCALLAPI
NTSTATUS
NTAPI
ZwQueryDirectoryFileEx(
    _In_ HANDLE FileHandle,
    _In_opt_ HANDLE Event,
    _In_opt_ PIO_APC_ROUTINE ApcRoutine,
    _In_opt_ PVOID ApcContext,
    _Out_ PIO_STATUS_BLOCK IoStatusBlock,
    _Out_writes_bytes_(Length) PVOID FileInformation,
    _In_ ULONG Length,
    _In_ FILE_INFORMATION_CLASS FileInformationClass,
    _In_ ULONG QueryFlags,
    _In_opt_ PUNICODE_STRING FileName
    );

#endif

View code on GitHub

This function is documented in Windows Driver Kit here and here.