I found that we are on Window and that is the reason above given command is not working for me. can you help, how can we convert this into windows executable command?

Yes, I have tried $ZF(-1 with other commands like mkdir and dir. It is working as expected and actions are done. So I think, we don't have issue with $ZF(-1).
But This might be a catch, I am not sure whether Xargs and Zip are installed or not. Currently we are using Unix/Aix machine, Could you please let me know how to install Xargs and Zip?

No, $ZF(-1) is returning 1 which is unsuccessful for following line.  
set cmd ="cd "_fileDirectory_" && find . -type f | xargs zip .."_ext_xlsxFile
Is there any other way for doing the same what this command is doing?

Actually  I have executed this only the cache prompt and do not have facility to access linux/unix directly. but I executed this command separately with $ZF(-1,cmd), there also it is not executing successfully and returning 1.