Why am I being asked for an employer's zip code since I am retired?

Where in the program are you encountering the question? Did you accidentally enter something onto a W-2? 

 

If you are retired and entering Social Security or retirement income you are probably in the wrong place in the software if it is asking you for an employer's address.

 

Do not try to enter your

SSA1099 

or RR1099RB as a W-2.  Go to Federal> Wages & Income>>Retirement Plans and Social Security  (SSA1099 and 1099RRB) to enter your SSA1099.

 

To enter your retirement income, Go to  Federal> Wages and Income>Retirement Plans and Social Security>IRA  401 k) Pension Plan Withdrawals to enter your

1099R.