Hi, Hope you are well!
We have worked with zapier. We also have experience in PHP/Python which we can use to write any custom code scripts if needed. We can help you in the best way with our previous experience and experts skills. Which API you will be needing us to integrate. We can combine both new subscriber and scheduled message to complete the action.
We have gone through the Hootsuite Triggers, Searches, and Actions are supported by Zapier.
We would request you to share more details on your use case and which APIs should be targeted.
Best Regards,
Murtuza S.