ZenCart for selling subscriptions

Hi, I'm new with ZenCart.

I want to use ZenCart as a storefront where users can browse and handles payment for several subscription types to another site (a subdomain). While "subscription types" AFAIK can be treated as virtual products with ZenCart, my question is this:

1. Subscriptions means recurring payments and invoices. I am reviewing some specialized billing system CMS because there are requirements for handling offline business as well. Are there some which ZenCart compatible or the dev team recommends?

2. Related to #1, after the payment is verified, how can I automatically transfer the details to the billing system and generate the login for the other site? I have no problem writing PHP, just where I should start looking.

Thanks