Zakah should be paid from both the capital and its profits
The Zakah is due on the money that you possess and on its profit after the passage of the Hawl on the capital while it is a Nisab (the minimum amount on which Zakah is due) or more (Part No. 8; Page No. 329) and regardless the sales are on installment or not.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.