Hello, I have worked with the Zoho One suite for 2 years and I have the experience for your project to develop as you desire. Automation, connections, workflow creation, field customization, everything that the Zoho One license has to offer can be done.
Sorry, but the description had me thinking on this question:
You are making a payment gateway website and need to connect it to Zoho's Apps?
Contact me so we can discuss your needs.
Greetings!