We are all part of God’s immense and extraordinary plan which, according to His will, strives always and everywhere for mankind's total well-being and happiness and yet is, at the same time, always and completely open and respectful of individuals' responses. Being in God's plan and acting according God's will are not the same thing.
The archangel Gabriel who defined himself: "I am Gabriel, who stands before God. I was sent to speak to you and to announce to you this good news,” is part of God's plan and carries out the will of the Father. Zechariah's doubtful, almost disrespectful answer is part of God's plan, which fully respects every free human response, but it is not part of God’s will since He would never desire such a doubtful response to a divine message of utmost importance for the salvation of the entire cosmos. Zechariah's speechlessness is not a punishment but a disharmony which can occur in humans when there is a dichotomy between the divine plan and divine will. Zechariah's doubtful answer is certainly part of God's plan, which foresees man's free response, but it is not part of God’s will. Man can achieve harmony and peace when he/she succeeds in a loving manner to become a part of God's plan and does so according to God’s will.
Managing the earth's resources in a harmonious and just way for the welfare of all men is God’s will, but because of the incredible freedom given to man even the disharmonious and incorrect response of polluting the air and water becomes a part of the divine plan.
Jesus, the beloved Son, killed and tortured on the cross, became part of the Father's plan, but it was not of His will. In the same way, human disease became part of God’s plan but it is not and will never be the result of His loving will. The same is true for death. Death is part of the God's immense divine plan, of man's free response, but it is not, and will never be part of God's will, desire and plan. The Word of God on this is clear and unambiguous. In fact it is written in The Book of Wisdom 1:12-15: Do not be responsible for people’s ruin with the error of your life, do not cause destruction by the works of your hands, because God did not create death, and he does not delight in the death of the living. From The Book of Wisdom 1:12-15: Court not death by your erring way of life, nor draw to yourselves destruction by the works of your hands. Because God did not make death, nor does he rejoice in the destruction of the living. For he fashioned all things that they might have being; and the creatures of the world are wholesome, And there is not a destructive drug among them nor any domain of the nether world on earth, For justice is undying (Literal translation from the Greek text). And we read in The Book of Wisdom: But by the envy of the devil, death entered the world, and they who are in his possession experience it (Literal translation from the Greek text).