Why are there two different equations to calculate standard cell potential

E0cell can be calculated using

E0cell = E0reduction + E0oxidation

and

E0cell = E0cathode - E0anode

they are the same

oxidation = anode
reduction = cathode

Because what happens at the cathode IS reduction.

Remember this SOAC/GERC (soac a gerc)

It stands for: Strongest Oxidizing Agent at the Cathode / Gain of Electrons is Reduction at Cathode.