Actually, the text I am reading off that web-page on my monitor says:
"Letter to 24-in wide sheets" for the 24" model and "Letter to 44-in wide sheets for the 44 inch model. "Letter" in North America is 8.5 by 11 inches, which is slighter wider and slightly shorter than European A4. This link is to the US website. It will most likely print A4 for the European models, but you can verify the specs for machines delivered in Europe.
Yes, the Z series accepts European DIN A4 size. I recently printed this size on my NEW Z3100.
I can truly second what michael said in his review (at least about the documentation and specs, exept about print quality, because unfortunately I did have no time at all during the last week since the delivery of my Z3100 and the only prints I made were two profiling prints )
Just one more thing to say:
Dont try to calibrate and profile on DIN A4 paper, the profiling chart needs to have an DIN A3 paper size. It is printed after the calibrating chart (which is DIN A4) is read by the spectro. It brought some headache to me, because profiling was not successful. Simply use the 24 roll for your first profiling
Not noticed by Michael is the paper sheet fed. You can only feed a single sheet of paper (which is no problem for my workflow), but you also have to feed it free hand without a corner to lay along (ähh, sorry for my English, guess I am missing the right word... no dictionary around ). Then the printer corrects the angle, but is only able to do this in a small amount. If fed incorrectly the printer rejects the sheet. This might take 1+ minute, if fed incorrectly 2-3 times. This is something to do better for HP, although of course it is a minor point.
Best regards from Cologne...