I have one hand, and I agree with Kers that the Z7 is a nice one-handed body - Fujis work well, too, while Sony and Canon can rarely resist putting something critical on the left shoulder of the camera. It's just a nice body to use in general. The lens designs are refreshingly small and light for the combination of performance and sensor size. Nikon has chosen to sacrifice maximum aperture and accept electronic distortion correction in return for some small, light and high-performing lenses. It's an interesting trade, not for everyone, but a good one for my particular use.
I like to do landscapes well out in the backcountry, and am always looking for "how much image quality can I haul for how little weight". These compact Nikkors with very good to excellent performance coupled with the Z7 body revolutionize what I can get out there. The body and lenses are all very small and light for the level of performance they offer. Anything lighter won't perform as well, although lighter options exist - and anything else with no-compromise 2019 performance is going to be heavier.
The D850, 14-24 and most recent 24-70 are (roughly speaking), a kilogram each. The 24-70Z and 14-30Z are half a kilogram each, and the Z7 is only a bit over that - half the weight for the same or better IQ (losing a stop but picking up an excellent in-body image stabilizer) is pretty compelling.
Outside of Nikon, a comparable Sony FE system will be about 250 grams heavier and lose some of the weather sealing (which is why I never bought one) - but it'll pick up a little bit of wide angle and quite a bit of telephoto in compensation. The A7rIII is about 20 grams lighter than the Z7, but the Sony 12-24 is about 80 grams heavier than the Nikon 14-30 and the Sony 24-105 is nearly 200 grams heavier than the Nikon 24-70 (if you substitute the Sony "Zeiss" 24-70 for the 24-105, you can get the total weight to line up pretty much exactly, but at a significant image quality cost).
Neither Canon nor Panasonic gets as light as the Nikon, and neither one has a native mirrorless wide-angle yet. The heavy Panasonic bodies will always make the whole system much heavier (unless they change their philosophy and release a compact full-frame body) - and the initial Panasonic lenses are also big and heavy, although that could change at any time - the next lens out the door could be tiny. Nobody knows how heavy the Canon high resolution body will be, or how it'll perform. The announced 15-35mm is a f2.8 lens, which will probably be much heavier.
The highest quality Fuji APS-C lenses in the same focal length range plus the X-H1, the only stabilized body in the Fuji line, are actually a little heavier than the Nikon system (the X-H1 body is the same or a bit heavier if you count that the Nikon is carrying more shots worth of battery, the 10-24 f4 is lighter, but the 16-55 f2.8 is heavier). If you're willing to go down to an X-T2 or X-T3 (no image stabilization) and the variable aperture 18-55, which is a very good lens, but not like the Nikkors or the Fuji 16-55, you can save a few hundred grams (~1200 instead of ~1600)
Oddly, pro-grade Micro 4/3 (7-14 Pro, 12-40 Pro, E-M1 mkII) is barely lighter than the Z7 system. If you make different choices (ultralight consumer zooms and an EM5 series body), Micro 4/3 can get very light (you can get to around 800 grams with an E-M5 II, a 9-18 f4-5.6 and a 12-60 f3.5-6.3, all of which are also tiny) - but it isn't going to be making 40x60" prints. If you're willing to sacrifice some wide angle, a top-end APS-C compact with a zoom like the G1x mk III is also very light.