What is the ruling when witness testimonies regarding the recipient of a sale authorized under power of attorney differ by conditional addition?

Primary text

If one witness testifies the principal authorized him to sell to Zayd, and the other testifies the principal authorized him to sell to Zayd, or if he wishes, to Amr, the agency is established regarding the sale to Zayd, as the testimony agrees on the core transaction involving Zayd, and the conditional option granted to Amr does not negate the primary authorization, therefore it does not harm it.