It depends on what are you shooting
Personally I go for small- medium birds and 500-600 is the starting point
Currently I use a Z8 and an 180-600 and the lens is stacked to 600mm, I also have 500pf, I found them almost equal on the final shoot, but there is a difference in total weight , my current combo is about 3,3 Kgr and with 500pf it’s about 2,7 Kgr not a big difference, but there is.
I had Z50 before and with 500pf was an excellent combo for stationary birds on a total weight of 2,2 Kgr, that’s ideal for me.
I have in my mind the Z50 II to recreate with 500pf the previous excellent combo, but can’t go back from Z8 is a lot of a camera!
Either way you go you won’t miss.