'101/B/E/F and a '101ZD are entirely different animals. The 'ZD is very close to a 90x in terms of circuit design. 6146Bs in the PA, 8.9875MHz IF (vs 3.180), PBT and other QRM-fighting niceties added.
Yes, adding 11M to the later models was "challenging" as compared to simply plugging in a crystal and 'cutting the brown wire'. But their receivers are much improved, especially where the MkIII and '902 variants are concerned. Still, Yaesu sold an absolute metric ass-load of the B and E variants. One of my former coworkers - a ham - recounted a tale of an area truck stop wheeling dolly full after dolly full of those rigs to their showrooms in the mid 70s.