wplms does not modify any behavior of woo-commerce.
We just use woocommerce recommended hooks.
You can check this doc:
https://docs.woocommerce.com/document/checkout-field-editor/
If you want to show pincode and other fields here then we have an option for that.
please goto wplms -> miscellaneous ->enable remove extra checkout fields .
refer :
http://prntscr.com/8yg5nz
Set it to No and save changes
The extra fields will start showing on the page. But for other fields, please follow the doc