RtlIsZeroMemory - NtDoc

Native API online documentation, based on the System Informer (formerly Process Hacker) phnt headers
#ifndef _NTRTL_H
#if (PHNT_VERSION >= PHNT_19H2)

NTSYSAPI
BOOLEAN
NTAPI
RtlIsZeroMemory(
    _In_ PVOID Buffer,
    _In_ SIZE_T Length
    );

#endif
#endif

View code on GitHub

This function is documented in Windows Driver Kit.