I am seeing a pattern that the critical points obey.
In this problem https://web2.0calc.com/questions/urgent-pls-help_1 we have
\(\left(x + 2y+4z\right)\left(\dfrac 4 x + \dfrac 2 y + \dfrac 1 z\right)= \\~\\ 4\left(x + 2y+4z\right)\left(\dfrac{1}{x}+\dfrac{1}{2y}+\dfrac{1}{4z}\right)\)
The critical point in this case occurs at
\((x,y,z) = \left(1,\dfrac 1 2,\dfrac 1 4\right)\)
I.e. the first critical point coordinate is 1 and the ratio of the critical point coordinates is inverse of that of the ratio of the coordinates in the expression.
In the problem at hand we expect the y coordinate of the critical point will be such that
\(x^3 = 1 \Rightarrow x = 1\\~\\ 5y^3 = 1 \Rightarrow y = \dfrac{1}{5^{1/3}}\\~\\ 25z^3 = 1 \Rightarrow z = \dfrac{1}{5^{2/3}}\)
This would have been modified somehow if the denominator were not symmetric in x,y,z, but in this case it is.
Critical points are found by setting the gradient equal to zero.
You then have to determine whether they are minima, maxima, or saddle points using the second derivative test.
That's not exactly trival for 3 variables but there is a method for doing it.
https://calculus.subwiki.org/wiki/Second_derivative_test_for_a_function_of_multiple_variables