<?php
/**
 * Apply a different tax rate based on the user role.
 */
function wc_diff_rate_for_user( $tax_class, $product ) {
	if ( is_user_logged_in() && current_user_can( 'administrator' ) ) {
		$tax_class = 'Zero Rate';
	}

	return $tax_class;
}
add_filter( 'woocommerce_product_tax_class', 'wc_diff_rate_for_user', 1, 2 );