yeah XMSZ was probably one of the most poisonous palm strikes. The fact that it's poisonous makes it very deadly.
remember when LMC's poisonous internal energy went thru HIS YG? Her poisonous palm strike made YG weak already. XMSZ is worlds above her palm strike in terms of poison I think.
Actually I do think that XZ's internal energy is higher than ZWJ's. By how much? Don't know. Since ZWJ's internal was the highest of the condor trilogy trio, he'd rank the closest to XZ's internal. But I don't know how close.
Honestly no one in Trilogy could beat Jue Yuan (Z3F master) in terms of internal strength "straight up duel"..