Hi! @Kames thanks for the feedback! I try to explain the logic.
The zk-proof validation, which confirms the authority of the user operation to interact with a protocol, occurs when the function (e.g., takeLoan) is called in the first place.
The isValidSignature function is called on the smart contract entry point to ensure that the user’s operation is authorized within the context of the smart account.
This step verifies the authenticity of the user operation at the account level before any interaction with external protocols, enhancing security. This dual-layer validation ensures both the integrity of the account and the legitimacy of interactions with external protocols.