Daenerys, recognizing that Zoro was not the kind of man to swear fealty to anyone had matching earrings forged for them. Golden dragons that encompass the entire ear, the tail piercing through the ear lobe. Upon giving Zoro his she granted him the official title of the Commander of the Queen's Guard.

However, she makes it clear that the role comes with none of the restrictions that typically accompany the title in Westeros. Aware that such vows would, in his eyes, strip him of the very freedom he holds dear and a sign of faith that she does not feel the need to bind him in oaths in order to trust him with her life. It also ensures that he is more flexible in his movements, for she is well aware that there will be times when sending him into battle and keeping another of her trusted warriors at her side would be the best call. This is also why, when Ser Barristan Selmy joins her side he takes on the more traditional aspects of the role.

Naturally, Zoro is the one to point out that she would have to pierce her ear in order to wear the earing. Something she'd entirely overlooked and then gave him the honor of doing. (Not that he saw it as an honor since he was threatened the entire time) Icing her ear so that she wouldn't feel as much pain he used the very earing he'd just replaced as her starter one. Giving her time to adjust to the piercing before she began wearing the heavier dragon cuff.

While Danny and Zoro have both perfected the art of cuntily drinking wine while staring someone down Greyworm and Daario created a name for when they both do it simultaneously side by side in response to someone's truly idiotic words. 

Jon doesn't succeed in killing Daenerys. Instead, she goes on to rule Westeros after the burning of King's Landing. Shortly after her victory, she strips Tyrion Lannister of his title and bestows it to Roroaona Zoro. One of the last of her most trusted friends and advisors.