"I will praise Hashem with my whole heart"
Here, Rabbi Elazar shows how Yah (Yud-Hei) is included with Halelu (praise) in Haleluyah. He then speaks of the secret of the alphabet shown by King David in his praises, namely the supernal letters, and the letters of Malchut, and the secret of 32 paths of Chochmah. Praising God with one's whole heart, we are told, means with both the Good and the Evil Inclinations. We should give thanks to God for good and for evil, and, furthermore, say this thanks before everyone.
Here, Zohar is taking us more deeply into a teaching that has been slowly but steadily intensifying throughout 'Trumah' - the nature of evil. When we are told that we should give thanks for evil, we probably feel a shock wave of protest run through us. Are we not here to defeat and overcome evil? How can we give thanks for such blackness? In each act of victory over evil, man achieves a state of divinity. He unleashes the Godly spark of Light flickering in his soul. This truth can be seen in our physical world. Muscle tissue requires resistance and strain in order to grow stronger. A lit candle requires darkness to give it value and worth. Likewise, the soul of man requires burden and darkness in order to realize its full splendor.
When evil has run its course, and man has fully triumphed over the darkness, the soul will be strengthened to its maximum potential. We will have evolved to the highest level - the state of God. This has been the journey of over 5761 years, thus far. Two paths to this ultimate divine place have always existed, the path of torment and the softhearted path of spirituality. Both paths strengthen the soul and achieve the same outcome. But the path of torment is known all too well, while the path of spirituality remains the least traveled, until now. By utilizing the awesome spiritual influence of the Zohar, we now choose the path of Light. We fully correct our souls and complete the spiritual evolution of all mankind in a compassionate way, so there is no further need of darkness and challenge.