code: public static INDArray normalizeZeroMeanAndUnitVariance(INDArray toNormalize) {
          INDArray columnMeans = toNormalize.mean(0);
          INDArray columnStds = toNormalize.std(0);
  
          toNormalize.subiRowVector(columnMeans);
          //padding for non zero
          columnStds.addi(Nd4j.EPS_THRESHOLD);
          toNormalize.diviRowVector(columnStds);
          return toNormalize;
      }
docs: Normalize data to zero mean and unit variance
  substract by the mean and divide by the standard deviation
  
  @param toNormalize the ndarray to normalize
  @return the normalized ndarray