Yes this is not sure whether any of parameter will contain value or not except @city or @zip.

and also I guess IN clause won't work with a variable containing multiple values

like the following code will not work:

select blah from blah where countryId IN (@country)

You can use the below query if a variable containing multiple values,

select blah from blah where

CHARINDEX(LTRIM(RTRIM(CountryId)), @country) > 0