My lightweight travel kit has a D500, D7200, 500 f5.6, 300 f4E, TC-14E III and Sigma 18-35 f1.8 in a MindShift Gear Backlight 18L. Two lenses that may substitute for the 300, are the Nikkor 70-200 f4 and 70-300 FX AF-P. The Z6 II/FTZ will replace the D7200 and the 24-70 f4 S will replace the 18-35. There are two big things I gain by adding the Z6 II, silent shutter and low light performance. I'm primarily a wildlife photographer and I have scared a lot of animals away with my D500 shutter going off. I really waited for the Z6 II to get the increase in buffer and better autofocus performance. I have the D500 for fast action, and am hoping that Nikon has a fast action DX mirrorless replacement in the next year or two when my D500 shutter finally hits the end of its cycle. The combination of DX and FX gives me a little more flexibility in focal length choice when using those lenses. Seems like the Z6 II will be the perfect compliment to my D500, and could back it up in a pinch.