I tried many times to shrink the picture, with various numbers of fingers in various directions. Since the OS isn't up, nothing much works. I have a BlueTooth keyboard and tried to enter the password from there but that, as expected, didn't work.
I haven't installed any new apps in some time. The unit had been sleeping several days but was fully charged when I picked it up and couldn't log on. I believe wi-fi was left on. Could the iPad have been wakened by wi-fi and some sort of update installed?
With the sign-in screen zoomed the only part of the keyboard that could be displayed was the region from the Q to the T of QWERTY, so I couldn't enter the whole password. After enough fooling around, I finally figured out that a three-finger swipe would move the view and I logged on. Having never used zoom, I was unfamiliar with the related gestures. Settings > General > Accessibility > Zoom explained that a three-finger double-tap turns zoom on and off. So that solved my problem and zoom is now locked off.
I must have clumsily made a three-finger double-tap while in the log-on screen to get into this in the first place.