Is $\frac{1}{(\textrm{can}-a-b\cdot i)^2}-\frac{1}{(\textrm{can}+\textrm{cod}-a-b \cdot i)^2}$ in any way simplifiable with Maple? So I wonder if Maple can reduce such lines like $$\frac{1}{(\textrm{can}-a-b\cdot i)^2}-\frac{1}{(\textrm{can}+\textrm{cod}-a-b \cdot i)^2}$$ (assuming all variables but $i$ are real)?

Writing $x = can - a - i\cdot b$ and $y = cod$, your expression is equivalent to
$$\frac{1}{x^2} - \frac{1}{(x + y)^2}$$
You could try reducing it to a single fraction:
$$\frac{1}{x^2} - \frac{1}{(x + y)^2} = \frac{(x + y)^2 - x^2}{x^2 (x + y)^2} = \frac{2xy + y^2}{x^2 (x + y)^2} = \frac{y(2x + y)}{x^2 (x + y)^2}$$
I guess you'll have to decide which one looks cleanest or works best for your purposes, but it will not get much better than what you had originally. 
