This is a comparison of the e-mount PZ18-105 to the ancient a-mount SAL 28-135 via the LA-EA4 adapter on the Sony a7RII.
Its an apples to oranges comparison because the e-mount lens is natively APS-C and auto-crops to 18MP instead of the FF 42MP we see with the FF 28-135.

In this case the APS-C e-mount was shot at 55mm and showed a similar FOV to the FF a-mount at what registered as 90mm. The camera placement was somewhat arbitrary.
While they both framed the test target similarly, at 100% the FF lens was much larger and we see it here also down-sampled to a similar size....unfair but real-world practical.

The focal length was arbitrary and as with most zoom lenses they vary focal length to focal length but this gives an idea of what generally happens.

The 35 year old FF lens obviously is providing more usable image information and also has a mechanical zoom.
In the 18-105G's favor is significantly better micro-contrast, image stabilization, some native functions like eye AF, a shorter MFD, a more compact form factor and the transmittance of the newer lens is better also. ...all non surprises.
The LA-EA4 also soaks up almost half a stop that has been compensated for in RAW development.