F mount Sigma 24-70 f2.8 sharp, until used with the FTZii adapter on the Z8

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So, the Sigma 24-70mm f2.8 I purchased to replace a Nikkor of the same type has been great when used with the D700 and D810, but I find it struggling with the Z8 using the adapter.

Some shots are still good, but they are normally right up close. The Sigma 70-200 f2.8 is fine though.

Anyone noticing similar issues?

I've not updated the firmware since I've had it as I don't own the dock for it, but not sure if that would make any difference anyway.
d810 36Mp
z8 45mp

clearly z8 is out resolving it which is hardly surprising at all. It is a zoom, an older zoom, and a widegangle to short tele made for dslr. Try some ART primes instead and report back.
The 70-200 f2.8 is older still but is still sharp, even handheld, as is the 50mm Sigma Art f1.4