Conceal works but not on some nested regions

Question

I'm trying to conceal the LaTeX command \footnote{} in a .tex file and show a bullet point instead. This works mostly fine, but when there is a \cite{} command inside the footnote, everything but the bibkey between curly brackets is concealed.

In other words this

\footnote{Some text.\cite{bibkey} And more text.}

becomes this

• {bibkey}••

Here is what I have put in my after/syntax/tex.vim

syntax region texFnZone matchgroup=texFnZoneDelim start="\\footnote{" end="}" contains=texStatement,texCite containedin=texChapterZone,texSectionZone,texSubSectionZone,texSubSubSectionZone,texParaZone,texSubParaZone conceal cchar=•
highlight def link texFnZone Todo
highlight def link texFnZoneDelim Todo

Question: how can I also conceal the curly brackets with the bibkey inside them?