# This works perfectly
$src = "C:\temp\test"
$dst = "C:\temp\test.zip"
[Reflection.Assembly]::LoadWithPartialName("System.IO.Compression.FileSystem")
[System.IO.Compression.ZipFile]::CreateFromDirectory($src,$dst)

# This fails with: 'Exception calling "CreateFromDirectory" with "2" argument(s): "Could not find a part of the path 'S:\test.zip'."
$user = "[username]"
$pass = ConvertTo-SecureString "[password]" -AsPlainText -Force
$creds = New-Object System.Management.Automation.PSCredential ($user, $pass)
$psDrive = New-PSDrive -Name "S" -PSProvider FileSystem -Root $sourcePath -Credential $creds
$src = "S:\temp\test"
$dst = "S:\temp\test.zip"
[Reflection.Assembly]::LoadWithPartialName("System.IO.Compression.FileSystem")
[System.IO.Compression.ZipFile]::CreateFromDirectory($src,$dst)