It's the general ellipsoid formula: x*2/a*2 + y*2/b*2 + z*2/c*2 = 1, where a, b and c are all unequal. The interesting part is actually that this shape could be made of a liquid, held by gravitation and maintain this asymmetrical shape. Normally, one would imagine it would be ellipsoid of revolution, where two of the axes are equal.

https://en.wikipedia.org/wiki/Ellipsoid

To make a plot in software such as JMol, you really need parametric equations, which are also given in the above page.