Dear Daniel, Thanks a lot for your suggestions. I realize that I don't know a lot about mathematica. Well, I put your suggestions in practice with excelent results.
I only made one addition: the non-simplified problem uses 400000 iterations instead of 10000. So, I made four separate process (for each of my cores) with ParallelSubmit, and reduce the calculation time almost ten times (!! I did not think this was even posible), from near 500 seconds to 50 seconds.