What are some extremely difficult chemical equations to balance

I think it's fun and easy balancing equations and I want a challenge! Not something simple like Fe2O3 + CO yields Fe + CO2. I want something hard!

Give this one a try:
(Cr(N2H4CO)6)4(Cr(CN)6)3 + KMnO4 + H2SO4 --> K2Cr2O7 + MnSO4 +CO2 + KNO3 + K2SO4+ HOH under acidic conditions

calcium phosphatge + silicon dioxide + carbon --> phosphorus + calcium silicate + carbon monoxide

aluminum hydroxide + sodium hydroxide ---> sodium aluminate + water

sodium wolframite + sulfuric acid ---> sodium sulfate + tungstic acid