Transactional Emails via Brevo/Zapier

We would like a transaction email to be sent to a client upon their case being reviewed by our team. A task such as 'Case Review' would be completed on our CRM - following this, we would like a transactional email to be sent out to the client, which will continue to be sent every 48/72 hours until the client uploads the information we need into a gravity form that we provide. The gravity form asks for the clients email address, which can then be used to stop the automation of further emails.

We use for current flow/automations

CapsuleCRM
Zapier
Brevo

It would be great to get this done as soon as possible - therefore price and timescale is needed.