Is this a custom installation, or is your translator distributed with
Zotero?
If the previous translator works on other sites and yours is just a
customized version for your own installation, you can just use a lower
priority.
If the previous translator was created specifically for your site, your
new translator should just use the same ID as the old one so that it
replaces it. If your translator is distributed with Zotero, your pull
request should be a modification of the old translator with the ID
unchanged.