Search Results: close to his girl best friend

There is my friend. Let's call him Z. So Z is a bit of a kid. He is not a kid but he acts like it. I usually ignore this and try to make him understand but today he crossed the line. So on Instagram, I followed someone and was talking to her. She is from another country and I don't know her much. He saw that I have been talking to her so he asked that "will she follow back?" I was like, "she might" but she doesn't talk much (she is an introvert). He was like, " should I follow her?" I was like okay but English is not her first language so you might not understand (she uses broken English sometimes). He said that he is not going to follow her or waste time on her. After then, when we met he told me that he had followed her and she had followed him back. I was cool as she is not that big of a deal. Today, he saw me talking with another girl. He asked me to show him my chats. I don't show people that. He told me to tell him her name. I didn't. I made it obvious that I don't want him to contact or know about her. He then searched and found her. He asked me more so I told him that she is from my best friend's college (I took my best friend's name) and he and my best friend are not that close of friends (just acquaintance). And my best friend don't like when his inner circle is violated and nor did I wanted him to talk to her or even follow her for that reason. So I told him to not send her follow request. He was like "okay, I won't!". Today I was talking to her and it was an intense conversation and then she asked me *who is my friend (name)?" I asked her why? And she replied saying that he had requested her. She then sent me a screenshot when I asked her. I am literally pissed. What the fuck is wrong with him?

P. s. he doesn't show me his texts with girls nor does he gives me their number or something and tells me that it's not right as he (my friend) is involved with them and they might think something is up or I might say something bad to them etc.