I just started to build cnc router with 2 Z axis , Please tell me how I connect the 2 Z axis to work separately. My  cnc driver  is g540  

Did you ever get a single axis to work correctly on your mill using the G540?  
Now your venturing onto a 4th / different machine.

RICH

not, it seems that it is not possible I have no more power, to annoy myself I have submitted myself, with gecko g540 I worked already 4 years , and never the driver worked well.

 I know that someone will say (This guy just does not know how to set the cnc machine!) This is not true! , For 4 years there is no possibility, so you did not learn what's come on in this.
Is there any problem, but I do not know what , and the worst part is that no one know what the problem is

I want to check once more g540, so I decided to build this cnc router with 2 Z axis. the only problem I have is if I will be able connect the 2 Z axis separately
I mean 1 to Z axis and the second to A or to B  i dont know

what are you building, any why?... and I see that as a programming nightmare.

MACH3 only has 1 z axis. IF you want to build duplexed version you are on your own.

(;-) TP

ok I see that there is no other option, it means I have to disconnect from one Z axis  motor cable , and connect the other motor. I am building a cnc router with plasma ,on one Z axis  will be plasma on the second Z axis spindle.
and that is why I wanted to work 2 Z axis separately.
does this mean? after working with plasma, machine will have to go to zero, rewarded the cables and start the spindle axis?

Then your not using a ROUTER your building a dual headed plasma cutting machine. That I would think you could do with one Z axis head and two digital height controllers. But your on your own with that. 

Maybe you could create two separate profiles.
One for Plaz, and one for Rout.
Then you would only need 1 Z axis.
Just jog the one you are not using clear of the work area.
Possible ?
Russ

YNN,
  I think maybe you misunderstood.
"""I am building a cnc router with plasma ,on one Z axis  will be plasma on the second Z axis spindle."""

Then you would only need 1 Z axis.
 

I mean 1 z per config.
Sorry for any confusion