What is ZTNA under the hood?

I see lots of vendors taking about how the VPN is going to die, but technically isn't this just a complex web of split tunnel VPNs that flow through the zero trust exchange of the vendor such as zscaler and then out either to a corporate internal network, a public cloud or SaaS or wherever on the internet?

I realise the protocol might be different and also the greater granular access control and visibility is an important development, but conceptually …

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