Add release note

RELEASE.md

@@ -20,4 +20,39 @@ Inspect formatting changes in the files listed above.
 
 There are no functional changes to the model. In the expectation files, global keys and references have been updated due to a bug fix, but they remain semantically the same.
 
-The changes can be reviewed in PR [#2550](https://github.com/finos/common-domain-model/pull/2550).
+The changes can be reviewed in PR [#2550](https://github.com/finos/common-domain-model/pull/2550).
+
+# *Product Model - Qualification Functions for Zero-coupon Swaps*
+
+_Background_
+
+The qualification function for a zero-coupon swap is too restrictive in CDM, since it requires that all the payout legs should feature one unique payment at Term. Normally a zero coupon only points out that at least one leg has a unique payment made at term.
+
+This release fixes this, along with some inaccurate provisions of qualifying functions regarding zero-coupon swaps. In addition, a new `Qualify_Transaction_ZeroCoupon_KnownAmount` function was added to facilitate the classification of Zero Coupon swaps with a Known Amount.
+
+This release also removes the use of conditional synonym mappings from FpML to CDM of the `PrincipalPayments` element for Zero-Coupon Swaps with Known Amount cases. The `Qualify_SubProduct_FixedFloat` qualification function has also been updated to not require the use of this `PrincipalPayments` element.
+
+_What is being released?_
+
+- Minor changes to existing Zero-Coupon Swap qualification functions
+- Addition of a new Zero-Coupon Swap Known Amount qualification function
+- Removed the conditional synonym mappings from FpML to CDM for the PrincipalPayments element in scenarios with Zero-Coupon Swaps with Known Amount.
+
+_Qualification_
+
+- Updated `Qualify_Transaction_ZeroCoupon` function to accurately qualify Zero-Coupon swaps.
+- Updated `Qualify_SubProduct_FixedFloat` function to include Zero-Coupon swaps with Known Amount.
+- Updated `Qualify_InterestRate_IRSwap_FixedFloat_ZeroCoupon` function to include Zero-Coupon swaps with Known Amount.
+- Updated `Qualify_InterestRate_InflationSwap_FixedFloat_ZeroCoupon` function to include Zero-Coupon swaps with Known Amount.
+- Created new `Qualify_Transaction_ZeroCoupon_KnownAmount` function.
+- Updated the annotations of `Qualify_InterestRate_IRSwap_FixedFloat_ZeroCoupon`, `Qualify_InterestRate_InflationSwap_FixedFloat_ZeroCoupon` and `Qualify_InterestRate_InflationSwap_Basis_ZeroCoupon` functions to accurately describe the qualified products.
+
+_Translate_
+
+- Deprecated use of synonym mapping from FpML to CDM for the `PrincipalPayments` element for Zero-Coupon Swaps with Known Amount cases.
+
+Review directions
+
+In the CDM Portal, select the Textual Browser and inspect each of the changes identified above.
+
+Inspect Pull Request: https://github.com/finos/common-domain-model/pull/2560