Does anyone know if big four accounting firm would withdraw I-140 if you leave within 6 months of approval?
Nobody has time to revoke I140. But, if you really pissed of your manager, burned bridges and stole and publicly shared some trade secrets then yes they will come after you. Revoking is a process in itself and costs money.
Repay the cost and they probably won’t
Technically you can't withdraw I140
Oh then it's possible and why would you leave before then? After 6 months the date is yours to keep/transfer
It's not (legally) mandatory for employers to revoke I-140 in the 6 months, in-case you leave..but they are "suggested" (as per guidelines) to do so in the event an employee leaves within the 6 months. Long story short: not worth the risk OP.
They cannot withdraw after 6 months of approval according to current law.