Here is a simple usecase: I would like to use fastmail for their mail offer on my own domain, but not for their calendar and contacts. I need something to keep

Here is a simple usecase: I would like to use fastmail for their mail offer on my own domain, but not for their calendar and contacts. I need something to keep my google calendar and contacts in sync with icloud calendar and contacts, with bonus points if it keeps that in sync too with outlook calendars and contact. (By keeping in contact I mean 2 way sync) I haven't seen such a product yet. What I would like is to have this mix of fastmail + the calendar and contacts gmail accounts on ,y desktop computer, and another mix of fastmail plus the icloud contacts and calendar accounts on my ipad and have both synchronize their data. Fastmail makes sense because it's better, but the contacts/calendar offering not so. Icloud has great sync features (push etc) for apple hardware, gmail for android, and it's a pain when you don't move fully to an ecosystem or another. The closest thing I've seen is Nuevasync to add Exchange Activesync to regular gmail accounts, but I'd prefer leaving icloud sync in its own way on the ipad.