From Sahih Bukhari (Hadith 1451):
Narrated Anas:Abu Bakr wrote to me what Allah's Messenger (ﷺ) has made compulsory (regarding Zakat) and this was mentioned in it: If a property is equally owned by two partners, they should pay the combined Zakat and it will be considered that both of them have paid their Zakat equally
Reference: Bukhari 1451