Is it possible to modify form fields of Shipping Address and Billing Address?

[Preetish_Hs]

I was wondering if its possible to retain Pin/Zip code to countries like UAE and Hong Kong? 

As soon as I select those countries ZIP code field disappears.

Also Add Provice field to when the country is Israel and Saudi Arabia? I need these captured to pass to Shipping partner.

If its possible, Which file should I edit exactly? I looked into checkout.liquid file but couldn't figure out what to edit there. 

Thanks!