If you run a load test with ZebraTester, if is possible to get quite a few metrics from the completed test so you can analyze this data in an external application. You can export Load Test Result data after a test has finished by clicking the "Export" button from the "Load Test Result Detail - Statistics and Diagrams" page (Load Test Jobs button from the main GUI):

In the "Export Load Test Result Detail" page, you can export data by Page, URL, or Sampling Data. If you export the data as an HTML table, you can open the file from Microsoft Excel and work with the data directly. In this example, I have calculated the sum of the "Average Response Time (ms)" of all the URLs in the load test:

I got this information by selecting these boxes in the Export Load Test Result Detail pane: