Run the following commands to reset the authorities and biblios Zebra indices.

$ zebraidx -c /etc/koha/zebradb/zebra-authorities-dom.cfg -g iso2709 -d authorities init 
$ zebraidx -c /etc/koha/zebradb/zebra-biblios.cfg -g iso2709 -d biblios init 

If you are running a package install then you'll want to run the following commands to reset the authorities and biblios Zebra indices instead:

$ sudo zebraidx -c /etc/koha/sites/YOURLIBRARY/zebra-authorities-dom.cfg  -g iso2709 -d authorities init 
$ sudo zebraidx -c /etc/koha/sites/YOURLIBRARY/zebra-biblios.cfg  -g iso2709 -d biblios init 

Replacing YOURLIBRARY with your Koha installation name.