How to rename woocommerce-billing-fields

Copy

\woocommerce\templates\checkout\form-billing.php

and

\woocommerce\templates\checkout\form-checkout.php

to

\yourtheme\woocommerce\checkout\form-billing.php

find this code <h3><?php _e( 'Billing & Shipping', 'woocommerce' ); ?></h3> in form-billing.php and <h3 id="order_review_heading"><?php esc_html_e( 'Your order', 'woocommerce' ); ?></h3>

and make the necessary changes .

Hope you are not doing this for anything regarding to I18n.