I'm happy to report another open source computer algebra system said my input equals zero.
You can see this is so at Bash's shell command line with $ mathomatic -e "((a - b) - (((a - b) + (c - d) + (e - f))/3)) + ((c - d) - (((a - b) + (c - d) + (e - f))/3)) + (e - f) - ((a - b) + (c - d) + (e - f))/3" simplify At least on my computer, it returns (a - b + c - d + e - f) (a - b + c - d + e - f) (a - b + c - d + e - f) #1: a - b - ----------------------- + c - d - ----------------------- + e - f - ----------------------- 3 3 3 #1: 0 If you happen to have the time, and are so inclined, I'd be interested in your thoughts on whether Poly() might be improved by distinguishing between GeneratorsNeeded: Cannot initialize from 'dict' without generators and its input equaling 0. I think the relevant code may be near line 250 in /usr/lib/python3/dist-packages/sympy/polys/polytools.py Thanks again for maintaining Debian's cool sympy package. Kind regards, Kingsley -- Time is the fire in which we all burn.