Delete Zip Folders in a Specific Directory when there are more than 4 in the directory using CMD Line Script

I have a script that backs up a database daily and zips up the files and stores it on a local drive. What I would like to do is then delete the oldest zip folder once there are more than 4 in the directory. The directory is D:\Temp\Backup. I inherited this script and am not skilled in command line at all. Any help with this would be great as I am not sure where to start. Due to the sensitivity of the script, I cannot share the existing code.

Thank you in advance.

I wrote onc sth like that.
It checks the folder for files older than 4 days, deletes all tfiles older and writes the filename into a textfile called "deletedlog.txt"

$Folder="D:\Temp\Backup"
Get-ChildItem $Folder -Recurse -Force -ea 0 |
? {!$_.PsIsContainer -and $_.LastWriteTime -lt (Get-Date).AddDays(-4)} |
ForEach-Object {
   $_ | del -Force
   $_.FullName | Out-File $Folder\deletedlog.txt -Append
}
Get-ChildItem $Folder -Recurse -Force -ea 0 |
? {$_.PsIsContainer -eq $True} |
? {$_.getfiles().count -eq 0} |
ForEach-Object {
    $_ | del -Force
    $_.FullName | Out-File $Folder\deletedlog.txt -Append
}