Symbols differ broker from broker. Sometimes you have to manually modify the AssetsFix.csv file in Zorro/History folder. See: http://zorro-project.com/manual/en/export.htm for asset list parameters description. Look especially at the "Symbol" column.

Also note that many brokers provide only very limited history. In that case you have to download the data from some other source, convert them to Zorro format, approximate and set your broker's parameters (again by modifying AssetsFix.csv file) and test with the new data and configuration. There's a conversion script for .csv files included in Zorro. For conversion to .t1 format and/or testing with floating spread I wrote these sripts: http://www.opserver.de/ubb7/ubbthreads.php?ubb=showflat&Number=464368#Post464368