I've never used a Hasselblad/Imacon Flextight (of any variety, let alone the newer X1), so I don't know how much difference a really good scanner makes, compared to a merely good scanner - but I've scanned quite a bit of medium format film with a Super Coolscan 9000 (long reputed to be the best scanner short of a Flextight), and I've had scans made on the $10,000+ flatbeds (I think it was a Fuji). Compared to either of those, I'd rather have a good Fuji (matters because Fujinon lenses are excellent) 24 MP APS-C file than a scan from anything short of 6x9 cm.
Your 645Z is producing a file that is the rough equivalent of scanned 4x5" film at low ISO, or at least my Nikon Z7 is, and the Z7 image sensor (24x36mm, 46 MP, but new-generation BSI CMOS) is a very close competitor of the older 50 MP CMOS sensor in the 645Z.
Unless the Flextight is extracting massively more detail than the Coolscan, which was showing film grain at full magnification, the race between 645 film and MF digital isn't even close. The Flextight will be lucky to get the overall image quality of a 24 MP APS-C digital capture (let alone >24 MP 24x36mm or medium format digital). Of course, there are really funky films that will get more than that (Tech Pan)...