I answered this question of yours over at StackOverflow:


  The logic through which controller class definitions are loaded builds the path to the file above the explicit include paths on which the autoloader relies. This means no local vs. core precedence. 
  
  You need to creat a controller rewrite by specifying a directory under the xpath frontend/routers/customer/args/modules/your_module
  
  The latter node needs the before attribute set to Mage_Customer and you will need to create an AccountController.php with a createPostAction() method. Depending on your needs you may or may not need to extend from and require the core account controller class. 


Error extends AccountController.php in magento
I have the following equation:

eq=E0[x,y,z]+E1[x,y,z]*Cos[phi]+E2[x,y,z]*Cos[phi]^2+E3[x,y,z]*Sin[phi]


Now E0,E1,E2 and E3 are already series expansions of expressions in x,y,z. Therefore I would like to series expand the result of 

Solve[D[eq,phi]==0,phi]


However, this is some giant arctan expression and Mathematica seems to take forever. 

Question: Is there a more clever approach to this (not calling Series at the end only), or is there some way I can tune the Series command?

Here are the real expressions I am dealing with, if someone wants to try something out:

Ecp = (s1*s3*Abs[J]/DE^2/2 - 1/DE*s2*s3*KroneckerDelta[1, s1])*(t1^2 -
      t2^2) /. KroneckerDelta[1, s1] -&gt; (1 + s1)/2 /. 
 t1 -&gt; tt1*DE /. t2 -&gt; tt2*DE /. xi -&gt; xii*DE /. J -&gt; Jj*DE
Ec2p = s2/DE^2*KroneckerDelta[1, s1] (t1^2 - t2^2)^2/Abs[J] /. 
  KroneckerDelta[1, s1] -&gt; (1 + s1)/2 /. t1 -&gt; tt1*DE /. 
t2 -&gt; tt2*DE /. xi -&gt; xii*DE /. J -&gt; Jj*DE
Esp = s2*s3/DE^2*t1*t2*xi*
    Abs[J]/(Abs[xi] KroneckerDelta[-1, s1] + 
       Abs[J] KroneckerDelta[1, s1]) /. 
   KroneckerDelta[1, s1] -&gt; (1 + s1)/2 /. 
  KroneckerDelta[-1, s1] -&gt; (1 - s1)/2 /. t1 -&gt; tt1*DE /. 
t2 -&gt; tt2*DE /. xi -&gt; xii*DE /. J -&gt; Jj*DE
Solve[D[E00 + Cos[phi]*Ecp + Cos[phi]^2*Ec2p + Sin[phi]*Esp, phi] == 0, phi]


The small parameters are tt1,tt2,Jj,xii. Usually I then introduce a "smallness-paramter" as suggested here on SE to perform the multi series.
