I have a circuit I am asked to find the equivalent resistance of. I have the schematic, but to be able to calculate the equivalent resistance, I have to prove that ICF=IDF=0. I have proven that ICF=IDF, IAC=IAD and ICB=IDB, but I cannot find any relation that would lead me to ICF=0.

I am familiar with Ohm's Law and Kirchhoff's two laws.

Any help is appreciated!