Your upgrades will be great with Zwift. It's GPU demands are pretty low, actually. Unless you want to see little details like headlight shadows at night. Up to you.
I'm running a multi-year old PowerSpec pc with an i3, a 128Gb SSD, and a ~$70 GeForce card. Looks great. The only thing I would change is the fans in the PC are
loud.
* the PowerSpec:
PowerSpec Support System Specs
* GPU
https://www.amazon.com/gp/product/B01AZHOWL0/