Provided the only error on your W-2 is the address, you can enter the correct zip code.
Did your employer mail the document to you? If so, look at the envelope it was sent to you in - does it have the correct zip code listed?
If not, you need to contact the employer and have them reissue a W-2 to you with the correct address. They also have the option to send the W-2 with the incorrect address, as long as the envelope the send the W-2 to you in lists the correct address.
Basically - the IRS just wants proof that your employer knows your correct address.
Read more: https://www.irs.gov/pub/irs-pdf/iw2w3.pdf page 25
