Unfortunately there is no support for different keyboard mappings yet. This feature is on our to-do list, but we haven't been able to come up with a good way to handle this in a way that is user-friendly and emulator-friendly at the same time.
Right now the only way to get your own keyboard mapping is to change the code in KEYBOARD.ASM and recompile it. I think there is someone who has already done that for MAME compatibility, but I'm not sure if he distributes his version of z26.
Ciao, Eckhard Stolberg