Changing lawyers before the trial has no effect on the case. The judge of the second instance often looks at the materials of the first instance and does not pay attention to the power of attorney of the second instance, so he often contacts the lawyer of the first instance.
Under normal circumstances, if there is no new favorable evidence, it is unlikely that the sentence will be changed in the second instance. Only by mastering new favorable evidence, the chances of changing the sentence in the second instance will be greatly improved. If the facts are clear and the applicable law is correct, if there is an appeal, the court of second instance will reject its application.