If an user will create zabbix DB without filling it by schema and will successfully perform the GUI setup, he will see a non friendly error text at the login page:
mysql_free_result() expects parameter 1 to be resource, boolean given [include/db.inc.php:561]

This error visible ONLY if a table "users" doesn't exist.
If the table "users" exists, we will see nice warning text: "Unable to select configuration." above the username input field.
And it still not very informative.

Would be great to check on step 3 is the DB created correctly and filled by data.
The check could be simple - presence of "users" table or more complex: at least one row in the "config" table.