Example code for cf_zapier_data filter. See: https://calderaforms.com/doc/cf_zapier_data/

cf_zapier_data-paypal1.php

<?php
/**
 * Send PayPal Transaction ID to Zapier when using Caldera Forms PayPal Express and Caldera Forms Zapier
 */
add_filter( 'cf_zapier_data', function( $data) {
   global $transdata;
   if( isset( $transdata['paypal_express'], $transdata['paypal_express']['result'] ) ){
       if( isset(  $transdata['paypal_express']['result']['PAYMENTINFO_0_TRANSACTIONID'] ) ){
           $data[ 'TRANSACTIONID' ] = $transdata['paypal_express']['result']['PAYMENTINFO_0_TRANSACTIONID'];
       }
   }

   return $data;
});

cf_zapier_data-paypal2.php

<?php
/**
 * Send All PayPal Transaction data to Zapier when using Caldera Forms PayPal Express and Caldera Forms Zapier
 */
add_filter( 'cf_zapier_data', function( $data) {
    global $transdata;
    if( isset( $transdata['paypal_express'], $transdata['paypal_express']['result'] ) ){
        $data[ 'paypal' ] = $transdata['paypal_express']['result'];
    }

    return $data;
});

Line 8 should be
$data[ 'paypal' ] = $transdata['paypal_express']['result'];