Folder being used for another process on batch script - powershell

Question

I have a issue with a backup script I wrote. The backup is pretty simple. It will copy a directory to a destination path, and then zip it. I have a few If clauses to, example, delete the oldest backup if there are 5 or more .zip from previous backups.
The problem I'm facing is: after the XCOPY command has finished running I then run a PowerShell script from my Batch to zip the backup, but I get this error:
This happens becaus the .bat file is running. I've checked.
The code for both the batch and power shell script follows:
BATCH:
echo "========================================="
echo "=====| Backuping DCT Light's Files |====="
echo "========================================="
SET dct-light_src=\\w102xnk172\c$\inetpub\wwwroot\DCT_NEW
For /f "tokens=2-4 delims=/ " %%a in ('date /t') do (set dct_light_startting_date=%%c-%%a-%%b)
For /f "tokens=1-2 delims=/:" %%a in ("%TIME%") do (set dct_light_startting_time=%%a%%b)
SET starttime=%dct_light_startting_date%
CD C:\Users\william_silva4\Desktop\tools_backup\dct_light\
SETLOCAL ENABLEDELAYEDEXPANSION
SET /A "N=0"
FOR /F %%f IN ('DIR /B /A:-D "*"') DO (SET /A "N=!N!+1")
IF %n% == 5 (
powershell.exe -noexit -file "C:\Users\william_silva4\Desktop\remove_oldest.ps1"
) ELSE (
IF EXIST C:\Users\william_silva4\Desktop\tools_backup\dct_light\dctlight_backup_%starttime%\ (
MD C:\Users\william_silva4\Desktop\tools_backup\dct_light\dctlight_backup_%starttime%\dctlight_backup
SET dct-light_dtn=C:\Users\william_silva4\Desktop\tools_backup\dct_light\dctlight_backup_%starttime%\dctlight_backup
echo A folder for this backup already exists. Beggining overwrite...
) ELSE (
MD C:\Users\william_silva4\Desktop\tools_backup\dct_light\dctlight_backup_%starttime%\dctlight_backup
SET dct-light_dtn=C:\Users\william_silva4\Desktop\tools_backup\dct_light\dctlight_backup_%starttime%\dctlight_backup\
)
)
CD C:\Users\william_silva4\Desktop\backup_completo
XCOPY %dct-light_src% %dct-light_dtn% /w /e /y /EXCLUDE:C:\Users\william_silva4\Desktop\backup_completo\exclusion.txt
For /f "tokens=2-4 delims=/ " %%a in ('date /t') do (set dct_light_finished_date=%%c-%%a-%%b)
For /f "tokens=1-2 delims=/:" %%a in ("%TIME%") do (set dct_light_finished_time=%%a%%b)
SET startdate=%dct_light_finished_date%
SET starttime=%dct_light_startting_date%_%dct_light_startting_time%
SET finishedtime=%dct_light_finished_date%_%dct_light_finished_time%
CD C:\Users\william_silva4\Desktop\tools_backup\dct_light\dctlight_backup_%startdate%\
echo.LOG of %starttime%'s Backup>LOG_%startdate%.txt
echo.Start time: %starttime%>>LOG_%startdate%.txt
echo.Finished time: %finishedtime%>>LOG_%startdate%.txt
CD C:\Users\william_silva4\Desktop\tools_backup\dct_light\dctlight_backup_%startdate%\dctlight_backup\
SETLOCAL ENABLEDELAYEDEXPANSION
SET /A "N=0"
FOR /F %%f IN ('DIR /S /B /A:-D "*"') DO (SET /A "N=!N!+1")
CD ../
echo.Files copied: %N%>>LOG_%startdate%.txt
powershell.exe -noexit -file "C:\Users\william_silva4\Desktop\zip_backups.ps1"
pause>nul
POWER SHELL:
#DCT Light's zipping
Start-Sleep -s 15
$source = "C:\Users\william_silva4\Desktop\tools_backup\dct_light"
$date = Get-Date -UFormat "%Y-%m-%d"
$destination = "C:\Users\william_silva4\Desktop\tools_backup\dct_light\dctlight_backup_$date.zip"
If(Test-path $destination) {Remove-item $destination}
Add-Type -assembly "system.io.compression.filesystem"
[io.compression.zipfile]::CreateFromDirectory($source, $destination)
Remove-Item $source\* -Recurse -Exclude *.zip
What I have tried to solve the problem:
Create a Master.ps1 with a list of scripts to run, where the first one is, obliviously, the backup batch file and then the zipping ps1 file.
Call the zipping ps1 file from the backup batch file on another window and then kill the batch. In this case, the first line of the zipping script was:
Start-Sleep -s 15
So I was certain that the batch was killed before I really started zipping.
None of the above worked. Any help? If nothing works I'll just schedule them as separated tasks on Windows.