I'm sure the information is available. TBD
I am guessing they are not jet engine; do they use hydrogen to generate electricity, or otherwise turn a propeller? If that is the case, they would (I think) be much slower. Given a choice of a six hour flight that destroys the planet and an eight hour flight that does not, plenty of people will pick the former.
Years ago they stated a target of "500-mile flights to serve the short-haul and commuter air travel markets".
"ZeroAvia prototype shown powering a 6-seat Piper M-Class aircraft, already in
flight tests from February 2019."
As of September 2022, together with Textron Aviation, there was a public announcement
to produce a hydrogen-electric engine for Cessna. If their ambitions meet their projected schedule, their ZA600 hydrogen-electric engine will power 9- to 19-seat aircraft with the aim of a 300 nautical mile range by 2025 and even a 40- to 80-seat aircraft with a range of 700 nautical miles by 2027.
Earlier in May 2022, a public announcement
was made with Mitsubishi to retrofit CRJ regional jets with hydrogen-electric powertrains.
"ZeroAvia says all flights by CRJ Series aircraft “should be zero-emission well before
the end of this decade.”