Answer,,,,,
The poster did it. It is very easy to create evidence of alibi. The poster first entered Zhang's house (with gloves, shoes, covers and equipment) and placed a large amount of bread with lethal sleeping pills in Zhang's house. Then he put a charcoal brazier and worked at the same time to create alibi. The poster was careful and did not Leaking out clues, predicting what will happen, sleeping pills and charcoal braziers are all confusing the police's attention. The owner is not present and can be evaded (doctors and carpenters cannot make simple mistakes and leave criminal evidence for themselves). Only those that seem irrelevant can be implemented.
