There is a Zapier trigger when a field is created, and a Zapier action to update existing records.
However, there is no Zapier trigger that uses a record being updated as a starting point.
For example, I can have a Zap that says when a new customer is added to my base, add them to a Mailchimp list. When the new record is added, I have a single select called ‘Status’. When the customer is added, this is set to ‘Lead’.
If this customer moves to ‘Dealt’, it would be great to able to move that customer onto a different targeting list on Mailchimp. However, because ‘When a record is updated’ isn’t available as a starting point, a lot of potential actions are ruled out.