simultaneously want to access both unix and window

I am trying to create script in which I can simultaneously access both Linux and Unix by using Powershell script, but I am facing problem whenever I run script it's opening Unix window but after existing from Unix session. I am able to access window session. I don't want to exit from Unix session. I want to use both. Please advise. Below is my code

[System.Reflection.Assembly]::LoadWithPartialName('Microsoft.VisualBasic') | Out-Null     
$prompt = new-object -comobject wscript.shell 
$getPasswordAIX = Get-Credential -UserName "Avni" -Message "Enter  password"
$passwordAIX = $getPasswordAIX.GetNetworkCredential().password
$userAIX = $getPasswordAIX.GetNetworkCredential().username

#.\plink.exe mlismbc014 -i H:\davinsi.ppk -l $userAIX -pw $passwordAIX
.\plink.exe mlismbc014 -i H:\Key\unixKeys\avni.ppk -l $userAIX -pw $passwordAIX
echo %errorlevel%

Write-Host "Press any key to continue ..."    
$anyKey = $host.UI.RawUI.ReadKey("NoEcho,IncludeKeyDown")    
$pshost = Get-Host              # Get the PowerShell Host.    
$pswindow = $pshost.UI.RawUI    # Get the PowerShell Host's UI.    
$newsize = $pswindow.BufferSize # Get the UI's current Buffer Size.   
$newsize.width = 150            # Set the new buffer's width to 150 columns.    
$pswindow.buffersize = $newsize # Set the new Buffer Size as active.    
$newsize = $pswindow.windowsize # Get the UI's current Window Size.    
$newsize.width = 150            # Set the new Window Width to 150 columns.    
$pswindow.windowsize = $newsize # Set the new Window Size as active.    
[System.Reflection.Assembly]::LoadWithPartialName('Microsoft.VisualBasic') | Out-Null    
$prompt = new-object -comobject wscript.shell