How to put aj item_display on mob?

Recently I've been trying to make a datapack with custom mob and for that I'm using Animated java. I tried to spawn item_display and the /ride it on mob that I need but it works only for the first item display, then I've tried to tp item_display to the nearest mob with the tag, but it works only for the first item_display too. Now I don't know what to do. I'd be very grateful if you could answer me! Mc version: 1.21.5