I was attempting to remove the & from the author list in the bibliography (for a new journal PeerJ):

> instead of this:
Roach NW, Edwards VT, & Hogben JH. 2004. The tale is in the tail: An alternative hypothesis for psychophysical performance variability in dyslexia. Perception 33:817 – 830.

> I wanted:
Roach NW, Edwards VT, Hogben JH. 2004. The tale is in the tail: An alternative hypothesis for psychophysical performance variability in dyslexia. Perception 33:817 – 830.

Editing the CSL in the Zotero Reference Test Pane, I thought I managed to remove it in the names macro, including and = "false", for example:

<macro name="author">
<names variable="author" suffix = ".">
<name name-as-sort-order="all" initialize-with="" sort-separator=" " delimiter = ", " and = "false"/>
</names>
</macro>

But when I installed the style and attempted to update my document, I received the following error:

Zotero Integration Error
Zotero experienced an error updating your document.
TypeError: this.and.single is undefined

Couldn't find anything directly related to this online so I went back to the code and removed "false". So the macro now looks like:

<macro name="author">
<names variable="author" suffix = ".">
<name name-as-sort-order="all" initialize-with="" sort-separator=" " delimiter = ", " and = ""/>
</names>
</macro>

I needed to restart word and then it was okay, displaying without the & in the bibliography.

Note: when debugging this in the Reference Test Pane, after I'd saved the CSL with the wrong coding and restarted, the example references wouldn't display or refresh.