Zero Lag is a modified EMA.

Calculation formula:

EMA ZL = α * (EMA + Gain * (Close - ZL [1])) + (1 - α) * ZL [1]
  

The formula is similar to EMA with an addition of a new value Gain * (Close - ZL [1])

Gain is the value selected from the interval [-GainLimit, GainLimit] to minimize the error for the current data sample (Close - ZL) → min

The indicator has three input parameters:

• Period - calculation period;
• Gain limit - the Gain parameter;
• Applied price - price used for calculations.