rows_offset() is an ORM method, you're constucting a query by hand, you should not do that, it's complex, difficult to maintain, and the way you are doing it, VERY insecure.
Read up on ORM crud queries, plenty of select examples in the docs...
$name and $where[] = array('name','=',$name); $email and $where[] = array('email','=',$email); $address and $where[] = array('address','=',$address); $zip and where[] = array('zip','=',$zip);
$query = Model_Customer::query();
count($where)===0 or $query = $query->where($where);