I wouldn't say he has a low midi-chlorian, his relationship with the force is often said to be clumsy, nothing(that I've read) has ever explicitly said that he has a low midi-chlorian count, all it is in my opinon, is that he never really focused on his training? if anything he's a little bit - not too much, below average, he's just a bit of a slacker and later becomes a more focused and adept Jedi, imo
Zayne was ernest and hard working IMO, but something of a screw-up even at non-force things.
And he did have visions.
I'd personally guess his count is sorta middle-of-the-road to below average, but he's untalented at using it / his natural aptitudes in the force don't favor normal usage.
Just as Corran has trouble with TK but good illusions, Zayne is bad at normal stuff but has some good uncontrolled visions.