Neuxel coined in @nonbinarysorcery means neutral-gender xenoic (xeno/xenic). But you can use as xeunine/neuxine, xeneu/neuxeno or nexeu. But mixing the both xingender and ningender into one identity is different. You can use nixingender/xiningender or as u said nexingender/xeningender. As both xeno and neutral have e in the labels, we could resume into eingender (as lingender and aingender was coined), but not sure if e could be used since other e-prefixed identities exist, such as epicenity. You can try using another letter ingender to coin.

Nixingender and xeningender sounds good tho.