As of right now, the Zendesk Zapier integration is missing quite a few functions listed in the Zapier API Documentation. In particular, community posts are not supported at all.
Zendesk does not currently support community posts in triggers and automations (Post on that issue). Adding community support in Zapier would be a great way to give Zendesk users a workaround, and it would open up so much functionality for external applications.
For example, I could hook up our company's DevOps account and create a Zendesk community post for every bug/feature request added into our DevOps backlog (or vice versa). I could even set up a custom function in Zapier to auto-create a Zendesk ticket when a community post is added and to reply to the post when an agent adds a reply to the ticket. It would cut out a lot of developer work on Zendesk's end and would allow users to easily create their own functions without much effort.
https://zapier.com/apps/zendesk/integrations
https://developer.zendesk.com/api-reference/help_center/help-center-api/posts/