How do i generate multiple invoice pdf files in one task?

i stuck on a problem generating pdf files. I have a module, which gets multiple invoice numbers. As a result i have to generate a single invoice pdf file for each invoice and create a zip file with all pdf files.

Is there an alternative using the PDF Model?

MagentoSalesModelOrderPdfInvoice

I can only run this 1 time to get the first invoice, a second run is not possible. And i dont want all invoices in a single pdf file.

foreach($selected as $id) {

    $invoice = $this->invoice->loadByIncrementId($id);

    $pdf = $pdfInvoiceModel->getPdf([$invoice])->render();

    $zip->addFromString($orderIncrementId.'_invoice.pdf', $pdf);

}

If soneone has a solution, this would be great.

Thank you in advance

Andreas