Is it ok to ignore the last 4 digits of the zip code in CKGS passport application form?

Hi Anil,
The CKGS website does not allow to enter the last 4 digits of the extended zip code (5 digit zip code + 4 digits) since the hypen character is not allowed.

Is it ok to ignore the last 4 digits of the zip code although the address proof contains the full 9 digit zip code (5+4 digits) ?

Yep, it is okay to ignore the last 4 digits. Only 5 digits are sufficient.