Do teleconverters reduce image quality?

Here is what the site says about that.

From Nikon Z 600mm f/4 TC VR S: Nikon Z 600mm f/4 TC VR S: A prime lens by Nikon for Full frame cameras, 600mm f/4. A pro wildlife lens with a built-in 1.4x teleconverter.

From Nikon AF-S DX 16-80mm f/2.8-4E ED VR: Nikon AF-S DX 16-80mm f/2.8-4E ED VR: A zoom lens by Nikon for APS-C cameras, 16-80mm f/2.8-4. A bright, high-quality DX standard zoom.

Quoted from this site's pages.