Questions about zero trust

Hi all,

I am looking for examples that implement zero trust networks in enterprise environment.

My current setup is basic:

• controller/router -> VLANs -> wifi clients / lan clients
• client are authenticated via radius
• local server is connected a VLAN which is also accessed via client-to-site VPN.

I am trying to understand:

• how does this replace site-to-site VPN?
• for client-to-site VPN, do I need to upgrade any part of my current setup.
• how would radius (802.1x) work in this system?

So basically, can I use zero trust for local networks?

Thanks, really appreciate it!