The speed of light and the passage of time cannot be treated as separate entities. They are one and the same. The fact that time slows in the presence of mass is a guarantee that the speed of light is not constant. The following is indisputable evidence in support of that claim.
A light ray is deflected off course as it passes by a large mass and the only way that can happen is if the speed of light on the inner edge of each wavefront (relative to the center of the large mass) is slower than on the outer edge. Otherwise, the angle of each wavefront would not be perpendicular to the ray's trajectory after the encounter. i.e. If the trajectory was shifted by 90 degrees by an encounter with a black hole, one plane of the wavefront would end up being parallel with the trajectory.
It can't possibly work even if a wavefront consists of a multitude of photons because the inner edge of the wavefront is still traveling slower than the outer edge and the wavefront angle could not remain perpendicular to the trajectory.
The previous equation, c' = (1-(2GM/r/c^2))c, gives a zero light speed at the event horizon of all Schwarzchild radii black holes, which fails for the same reasons as described above.
This equation, c' = c/(1+(2Gm/r/c^2)) gives a zero light speed at a point mass, and a halved light speed at every Schwarzchild radius.
This is how the two equations compare for the two radii from the Sun's center of mass given below.
M = 1.99E+30 new = c/(1+(2GM / 1.2e+9 / c^2)) = 299791720.085 old = (1-(2GM / 1.2e+9 / c^2)) * c = 299791720.084 new2 = c/(1+(2GM / 1.5e+9 /c^2)) = 299791867.668 old2 = (1-(2GM / 1.5e+9 / c^2)) * c = 299791867.667
Both equations bend light around the Sun at the specified radii at near enough to twice the speed with which matter is shifted, but that minor discrepancy has major consequences approaching the event horizon.
The speed of light is slowed in the presence of mass and that is an indisputable fact which is of consequence to the zero origin concept. I had assumed that the speed of light would increase around a black hole because that environment would be in a more advanced state of evolution. Instead it seems to be lesser advanced. The environment mimics the origin of the universe, where the speed of light was zero and mass potential was absolute. The emergence of anything more than absolutely nothing would represent instantaneous action and would be absolutely resisted. ???