Is Zapier acting as a subprocessor to Dastra (what is its contractual status)?
Zapier acts as a third-party organization in the implementation of automation and is not a subsequent processor for Dastra when you use Zapier to connect your information system to Dastra.
Zapier will, according to their terms of use, act as a processor on your behalf.
Does Dastra have documentation on the reliability of Zapier?
Zapier provides documentation on the use of its services, including reliability. The level of service may vary according to the plan chosen and Zapier's purchasing conditions.
For further information, we recommend that you carefully read the general terms of service (https://zapier.com/legal).