Sadly, there is no Zapier integration for WhatsApp. They have a page on the Zapier app directory, but it's currently marked as "Upcoming" and has been for a long time.
However, there is another way. Using Zapier and an app called WATI, you can send WhatsApp messages to your contacts and customers automatically.
Follow this helpful guide from WATI
Create an account with WATI. You'll need the 'API Gateway' plan which starts at $49/month.