NtCreateUserProcess - NtDoc

#ifndef _NTPSAPI_H
// User processes and threads
#if (PHNT_MODE != PHNT_MODE_KERNEL)
#if (PHNT_VERSION >= PHNT_VISTA)

NTSYSCALLAPI
NTSTATUS
NTAPI
NtCreateUserProcess(
    _Out_ PHANDLE ProcessHandle,
    _Out_ PHANDLE ThreadHandle,
    _In_ ACCESS_MASK ProcessDesiredAccess,
    _In_ ACCESS_MASK ThreadDesiredAccess,
    _In_opt_ POBJECT_ATTRIBUTES ProcessObjectAttributes,
    _In_opt_ POBJECT_ATTRIBUTES ThreadObjectAttributes,
    _In_ ULONG ProcessFlags, // PROCESS_CREATE_FLAGS_*
    _In_ ULONG ThreadFlags, // THREAD_CREATE_FLAGS_*
    _In_opt_ PVOID ProcessParameters, // PRTL_USER_PROCESS_PARAMETERS
    _Inout_ PPS_CREATE_INFO CreateInfo,
    _In_opt_ PPS_ATTRIBUTE_LIST AttributeList
    );

#endif
#endif
#endif
View code on GitHub

#ifndef _NTZWAPI_H

NTSYSCALLAPI
NTSTATUS
NTAPI
ZwCreateUserProcess(
    _Out_ PHANDLE ProcessHandle,
    _Out_ PHANDLE ThreadHandle,
    _In_ ACCESS_MASK ProcessDesiredAccess,
    _In_ ACCESS_MASK ThreadDesiredAccess,
    _In_opt_ POBJECT_ATTRIBUTES ProcessObjectAttributes,
    _In_opt_ POBJECT_ATTRIBUTES ThreadObjectAttributes,
    _In_ ULONG ProcessFlags, // PROCESS_CREATE_FLAGS_*
    _In_ ULONG ThreadFlags, // THREAD_CREATE_FLAGS_*
    _In_opt_ PVOID ProcessParameters, // PRTL_USER_PROCESS_PARAMETERS
    _Inout_ PPS_CREATE_INFO CreateInfo,
    _In_opt_ PPS_ATTRIBUTE_LIST AttributeList
    );

#endif
View code on GitHub