The Form 16 generation video that we already have explains the end to end process involved in your form 16 generation by uploading part A and part B document which you have downloaded from TRACES.
There may be situations where you find the part A and part B documents are not available for your zero tax employees since their income tax information may not have been added while filing the Form 24Q for the financial year. However, you can still generate part B documents for your zero tax employees on greytHR, since this document contains information about the income paid and the exemption details for the employee.