IsZeroAsAValue​(AngouriMath.​Entity)

Whether a constant in the symbols is zero as a value, decided as
InLowestTermsOverTheSymbols(AngouriMath.Entity) decides it: over one bar, its numerator
expanded is zero as written, as a number, or at two sets of pinned symbols. A
coefficient read off a written polynomial can be zero so and not as written:
-3 a^3 + 3 a^3, which the expansion of (-(a - a u^2) - (u^2 + 1) a)^3 leaves at u^6, and -(2 c/c - 1) + 1.
https://github.com/asc-community/AngouriMath/issues/1665