Counter offer advice

Hi All,

I have an offer from Cognizant with 21LPA (20.3 fixed + 70k variable) and other offer from Zensar with 22 LPA (21Fixed + 1L variable) + 1L joining bonus. But I am interested in joining cognizant joining date is 22nd May.

Can I now ask Cognizant to revise the offer with Zensar counter offer considering only 3 days left for DOJ ? And how much can I ask for revising the offer?

YOE: 8.5

Advice will be appreciated, thanks in advance.