<a href="path of zip file" download> Download </a>

$url = $templete_url .'download_theme/theme.zip';
$link = "<p><a href='$url' >Download</a></p>";

require 'PHPMailer/PHPMailerAutoload.php';
$mail = new PHPMailer;
$mail->IsSMTP();                                      // Set mailer to use SMTP
$mail->Host = 'smtp.gmail.com';                 // Specify main and backup server
$mail->Port = 587;                                    // Set the SMTP port
$mail->SMTPAuth = true;                               // Enable SMTP authentication
$mail->Username = 'email';                // SMTP username
$mail->Password = 'password';                  // SMTP password
$mail->SMTPSecure = 'tls';                            // Enable encryption, 'ssl' also accepted
$mail->From = $email;
$mail->FromName = '';
$mail->AddAddress('Emaial address', 'Name');  // Add a recipient
$mail->IsHTML(true);                                  // Set email format to HTML
$mail->Subject = 'Login Details';
$mail->Body    = $link;
$mail->Send();