dataverse_select_expand.ps1

$environmentUrl = "https://yourorg.crm.dynamics.com"
$accessToken = "YOUR_ACCESS_TOKEN"
$requestUrl = "$environmentUrl/api/data/v9.2/contacts?`$select=fullname,emailaddress1&`$expand=parentcustomerid_account(`$select=name,accountnumber)"

$headers = @{
    Authorization       = "Bearer $accessToken"
    Accept              = "application/json"
    "OData-Version"    = "4.0"
    "OData-MaxVersion" = "4.0"
}

$response = Invoke-RestMethod -Method Get -Uri $requestUrl -Headers $headers
$response | ConvertTo-Json -Depth 10