UPDATE:
Indeed - ABZXing lib works not only with ZXing, but also with Quickmark. Why the hell the Quickmark app did confuse me with strange characters instead of correct code? With my B4A app everything works, and at least with Code128 as fast as the ZXing.
It's a little bit annoying that some frames rotates indicating that QuickMark itself works in landscape mode (but it reads omni-directional) just before and after the scan.
Still not solved: How to integrate the scanner preview in a "window" on my app form instead of fullscreen. Since my cam has a wide view angle, the marked reading area (in ZXing as well as in QuickMark) would be enough to see.
An idea: If a scanner API will not work in this way, maybe I could use a cam view instead and start the scanner itself with an additional tap on it.
BTW: All this do not have to be fast - if I have to scan much codes in a short time, there's no way but using an external (bluetooth) hardware scanner - I have two of them ...