I had a few complaints about the available citation styles, however. I prefer Chicago style using short footnotes and bibliography, but no "ibid." For citing early modern editions, I think it's important to include an ISTC or VD16/17 number to unambiguously identify the edition, but there was no easy way to do that within Zotero. You can add it by hand, but that defeats the purpose of Zotero.
Solution: Create a new style by hacking the chicago-note-bibliography.csl file to suppress "ibid." and add ISTC/VD16 numbers to citations.
Suppressing "ibid." only required removing some lines of code. I added VD16 numbers to the
<macro name="STC index">(Updated to reflect helpful comments from adam.smith.)
The "bibliography" section was easy. I just added this line before the various "locators" (which means "page numbers" for books):
<text macro="STC index" prefix=". ">
The "citation" section was trickier, because Zotero wants to place commas in between everything. I had to remove the line that set the group delimiter to a comma, and then change the rest of the lines to the following:
<text macro="contributors-short" suffix=", ">
<text macro="STC index" prefix=" (" suffix=")">
<text macro="point-locators-subsequent" prefix=", ">
It's kind of an ugly hack, but now my footnotes look like this:
Pflaum, Ettlich weissagung (VD16 P 2401), f. b2r.