A photon has no mass. Newton's equation specified massive bodies. Ergo, Newton's equation does not apply to photons. Einstein's equation does apply to photon

A photon has no mass. Newton's equation specified massive bodies. Ergo, Newton's equation does not apply to photons. Einstein's equation does apply to photons. Ergo, Einstein's equation is not Newton's equation. For velocities much less than the speed of light, Einstein's equation is well approximated by Newton's equation.