Equal length plumbing is not that big a deal. Between the side suctions, yes, but for the returns , not a biggie. If you extend the return line by a foot or two beyond the more distant return and cap it, the returns will equalize. I see mas985 had the same idea.
That isn't quite what I had in mind. Capping one end of the line won't really help any to equalize the returns. I was suggesting using a loop where both ends of the pipe along the pool feeding the returns are connected to the main return pipe via a tee. Ideally the tee is halfway between the two end returns with each end of the tee feeding the outer two most returns.
However, if you are trying to make the paths to each return have the same head loss, you need to take the fittings into consideration. Each fitting type has an equivalent length of head loss. But because you have three returns, there will be an imbalance due to that as well unless you can find a three way split. One option is to split the line once with a direct route to the furthest return and a second split going to the closest two returns. But because one return has one split and the other two have two splits, the single split return needs to have an extra 12' of 2" pipe to compensate for the split it doesn't have. Then each of the three paths would have approximately the same head loss. If the single split line has an extra 90, then it would only need 6' of extra 2" line (45s are about 3' of 2" pipe). So depending on how you lay out the plumbing you can usually make the head loss close to equal.
