Why are w=fxd and E =mc2 both energy

Answer 1

The second law of thermodynamics: Heat is work, and work is heat.
The equivalence of mass and energy: mass is energy, and energy is mass.

These are fundamental laws of Physics. Believe them.

If you wish, you can work out the units in force*distance and mass*velocity^2, and prove they have the same unit, units of energy.

Answer 2

Ok ty