Turning into a cat was Zheng Qing's third plan.
Of course, to enact this plan, Zheng Qing still needed a proper excuse. Just like in his first plan, he had to give up his work at Greenhill Mansion because he needed to go to Old Yao's office; in his second plan, he was 'injured' during the practice class and was also forced to quit his job at Greenhill Mansion.
When he initially settled on the third plan, Zheng Qing did not think it was overly complicated.
He only planned to ask for a half-class leave during the practice class on Friday afternoon, then sneakily transform into a cat and directly slip into the forest behind the academy.
That forest was full of all sorts of small animals; a black cat hiding there was like a drop of water falling into a lake, causing not even a ripple. Zheng Qing could completely disappear from the campus without a trace.