Also, not sure if this was a typo or not, but:
if(!$email || !zipcode){
should be:
if(!$email || !$zipcode){
If you're trying to find if they had a value, you might be better off using a function:
if(empty($email) || empty($zipcode)){
shrug I never did like using things like "if(!$var)"... I don't know, just a preference I guess.