I'm in the U.S. There just aren't a lot of DIY Z owners around here. I'll get my son to assist...the Z will be his someday as the 3rd generation in my family to own it. I think the instructions are pretty clear and he and I are both pretty comfortable with tools. We do our own brakes and we've done upgrades to both the Z and his hot hatch Ford. From reading, this task just seems a bit....fussy and I know that every time I do something like this something goes wrong.
Installing the cat-back on the Z took triple the time it should have because we could not get those damn exhaust hangers to come off. We bent the specialized tool we borrowed in the process and had to go to the store to get a new (better) one. At least the guy who lent us the tool got a free upgrade!
I'll probably wait until it cools down a bit to do the work. Right now we're running temps in the mid-upper 90's (that's 35+ for you guys over the pond) and super high humidity. Not sure if it's a thing in Europe, but with the consistently high humidity here, which affects your body's ability to stay cool, we have what we call "heat index" which is what it actually feels like. Our heat index is over 100 (38) this time of year. That's miserable temps to try to do anything physical outside.