These are great pictures, sure. However none of these rely on the capabilities of a camera like the Z9.
Your friend (and most skilled photographers) could have clicked those pictures with entry level cameras paired with appropriate lenses.
There's no such thing as an image relying on the capabilities of a Z9. In terms of raw image quality, it uses the same-ish sensor as a high-end DSLR, say a D850. Resolution and dynamic range are highly similar.
A mirrorless system does not create better pictures. It does increase the likelihood that you capture the image you want at all.
> There's no such thing as an image relying on the capabilities of a Z9
Sure there is.
For example consider the problems involved in taking a high resolution picture for a fast moving but difficult to focus object in low light. A Z9 will do brilliantly but cheaper cameras -- not so much.
A camera is not just the image sensor, modern sensors are all fairly close technologically in the grand scheme of things.
I linked to his photos as a confirmation that he is an adept photographer whose opinion about a camera is valid. But, hey, the shots are—at the least—not worse than his pre-Z9 images.
https://www.instagram.com/timdurkan/?hl=en