The word processor plugins are bundled with Zotero and should be installed automatically for each supported word processor on your computer when you first start Zotero.
Note that Google Docs support is part of the Zotero Connector for Chrome and Firefox and requires the Zotero program to function. A version of the Zotero Connector for Safari that supports Google Docs will be available in the near future.
There is currently no good way to integrate Zotero with Scrivener.
Zotfile is a Zotero plugin to manage your attachments: automatically rename, move, and attach PDFs (or other files) to Zotero items, sync PDFs from your Zotero library to your (mobile) PDF reader (e.g. an iPad, Android tablet, etc.) and extract annotations from PDF files.
You might want to use ZotFile if you have ever hit the limit on the free Zotero storage. You can use ZotFile to easily rename and move PDFs; combine it with UVA's Box for unlimited cloud storage.
This University of Melbourne Research Guide nicely details the specifics of working with Zotero and LaTeX.
Overleaf is a cloud-based LaTeX editor. It's great for collaborative work in LaTeX.
Consider integrating Better BibTex into your workflow. This Zotero plugin will give you fine-tuned control of your BibTex citation keys.
R/RStudio users can greatly benefit from R Markdown's Visual Editor. The Visual Editor makes it easy to insert BibTex citation keys.
Python/Jupyter Notebook users may benefit from the cite2c plugin.
It is usually necessary to include a citation style language (.csl) file when working with LaTeX/Markdown/plain text editors. You can find them all at the Zotero Style Repository.
If you’re using a mobile device or a desktop browser without a Zotero Connector, you can use the Zotero Bookmarklet to save items to your Zotero library.
The Zotfile plugin allows you to use Zotero on a tablet.