Zoho Flow: How to make a For each logic to send email notifications?

Hello.

We need to develop a way to send Emails Notifications to a list of Contacts every X days. That list will change according to the information in CRM every time the Flow is triggered (basic diagram is attached below).

I've thought of creating a Flow that triggers on Schedule.
Then a Custom Function will get records from CRM and return a list of Contacts IDs.
The list's size can be up to several thousands in one trigger.
Lastly a loop will send a Zoho Flow "Send Mail" Notification template to every record.

Is this viable in Flow?

I have thought of adding Contacts to a Campaigns list and then sending a mailing campaign, but I encountered some problems:

A loop will still be necessary to add every contact to the list.
A loop will also be needed to delete every contact from the list since every time the Flow is triggered a different list of records will be fetched.

Thank you,

Sergio.