Zlib is breaking CodeIgniter Zip Downloader and PHPExcel

I'm facing an issue where if Zlib compression is enabled on the web server, downloading any zip file using CodeIgniter's force_download function in the system's download_helper.php file breaks the archive file and prevents users from opening it.

Here are the headers being used in the force_download function:

    header('Content-Type: "'.$mime.'"');
    header('Content-Disposition: attachment; filename="'.$filename.'"');
    header("Content-Transfer-Encoding: binary");
    header('Expires: 0');
    header('Pragma: no-cache');
    header("Content-Length: ".strlen($data));

Enabling Zlib also breaks PHPExcel by producing garbled characters in Excel files as you can see in this image.

Headers for PHPExcel download function.

ob_end_clean();                    
header('Content-Description: File Transfer');                            
header('Content-Type: application/vnd.ms-excel');                            
header('Content-Disposition: attachment; filename=' .$fileinfo['filename'] . '_' . $customerId . '_' . date("mdy") . '.xls');              
header('Content-Transfer-Encoding: binary');                            
header('Expires: 0');                            
header('Cache-Control: must-revalidate');                            
header('Pragma: public');                            
header('Content-Length: ' . filesize($file));                            
ob_clean();                            
flush();                            
readfile($file);

Is there a proper workaround to enable Zlib and not breaking these features?

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