遇到复杂的表达式就束手无策了，求大神指导

请问怎么把下面这段代码运算出的表达式，改造成如图所示一段一段的、整齐漂亮的样子？
expr10 = -(\[Rho]e1[x]/(\[Epsilon]r*\[Epsilon]0));
expr20 = -((\[Rho]e2[x] + \[Rho]fix)/(\[Epsilon]r*\[Epsilon]0));
\[Rho]e1[x] =
v*e*n*(Exp[-((v*e*\[Psi]1[x])/(k*T))] - Exp[(v*e*\[Psi]1[x])/(k*T)]);
\[Rho]e2[x] =
v*e*n*(SubPlus[b] Exp[-((v*e*\[Psi]2[x])/(k*T))] -
SubMinus[b] Exp[(v*e*\[Psi]2[x])/(k*T)]);
\[Rho]fix = z*e*N0;
expr11 = Series[expr10, {\[Psi]1[x], 0, 1}] // Normal;
expr21 = Series[expr20, {\[Psi]2[x], 0, 1}] // Normal;
l1 = DSolve[\[Psi]1''[x] == expr11, {\[Psi]1[x]}, x][[1, 1, 2]];
l2 = DSolve[\[Psi]2''[x] == expr21, {\[Psi]2[x]}, x][[1, 1,
2]] /. {C[1] -> C[3], C[2] -> C[4]};
cond1 = C[1] == 0;
cond2 = (l1 /. {x -> 0}) == (l2 /. {x -> 0});
cond3 = (D[l1, x] /. {x -> 0}) == (D[l2, x] /. {x -> 0});
cond4 = (D[l2, x] /. {x -> -d}) == 0;
sol = Solve[
cond1 && cond2 && cond3 && cond4, {C[1], C[2], C[3], C[4]}][[1]];
l3 = l2 /. sol // ExpToTrig // Simplify