@echo off
setlocal enabledelayedexpansion

if not exist z: (
net use z: /del /y
net use z: \192.168.1.100\backup "Passw@rd" /user:administrator
goto copyfiles
)else (
goto copyfiles
)

:copyfiles
echo %date%%time% Starting synchronize files... >> d:\log\%date:~0,4%%date:~5,2%%date:~8,2%.log
robocopy D:\Backup z:\ /mir >> d:\log\%date:~0,4%%date:~5,2%%date:~8,2%.log
echo !date!!time! Done! >> d:\log\%date:~0,4%%date:~5,2%%date:~8,2%.log