Hello Pankaj,
Are you applying for normal working visa or blue card?
If you plan to apply for blue card, you don’t need the ZAV pre-approval, also it will take less time for blue card application, to compare with normal working visa.
If you are applying ZAV pre-approval for your working visa, the Federal Employment Agency (Bundesagentur für Arbeit — or “BA”) will contact your employer once they receive your documents. They will discuss your case with your employer, so that you(and your employer) will know if you will receive the approval, or know the reason why they deny your application (if it happen).
PS: another suggestion is that visit the embassy with all the documents that will help your application, even if those docs are no required.
Wish you best :)
