This program, for example transforms the "z69JZ..." string into
5KZnsvrXDcP7JFD7GCuZvifrbcBtK4kAe8nHx6ibktgvPJxs4Lp
can you recheck please...
is your result ok?
cause i get a different result:
5KZnsvrXDcP7JFD7GCuZvifrbcBtK4kAe8nHx6ibktgvPJxs4Lp <-your
5KZnsarXDcPgJFD7GfuZvifEbEBtKLkAe8nSx6ibkygvPJxr4Lp <-my
or i have some error in my code, i dont know, cant find it...

Yours is wrong somehow. I can confirm that my code returns the same result as alphabetacanary's.