I've handled both, and the gen.
I'm perhaps a little biased as the ZF I got was m2m and caused me a load of problems. It's still in pieces a year later.
The ZF has indices that lift at the edges. This is incorrectly listed as a flaw - having tried on the gen, this was the case on that too. However obviously QC plays a part, some I've seen have been a little too lifted, it's very subtle.
There is a small difference in the dial - the J is very slightly different on the ZF, closer to gen.
Otherwise, I have to question if it's the same watch. Everything else is practically identical bar the Canon pinion and moonphase.
The moonphase is completely flat on the ZF. Unfortunately this is a glaring flaw. The moon is meant to be concave in texture. GF is not perfect but is much closer.
Flip the watch over and not much to see - a crappy miyota with some decoration.
It looks good from the front, you can be happy with both models, but for me GF is the one to go for.
Don't have any pics of my GF as it's in storage but I have an old ZF one, and gen here:
ZF
Gen
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