<<< mml $$S_{Q_4^3}^{P_2^1}=S_{Q_{4\phantom{\text{z}}}^3}^{P_2^{1\phantom{\text{z}}}}$$ >>> native [ ESubsup (EIdentifier "S") (ESubsup (EIdentifier "Q") (ENumber "4") (ENumber "3")) (ESubsup (EIdentifier "P") (ENumber "2") (ENumber "1")) , ESymbol Rel "=" , ESubsup (EIdentifier "S") (ESubsup (EIdentifier "Q") (EGrouped [ ENumber "4" , EPhantom (EText TextNormal "z") ]) (ENumber "3")) (ESubsup (EIdentifier "P") (ENumber "2") (EGrouped [ ENumber "1" , EPhantom (EText TextNormal "z") ])) ]