1 Day trip in Shenzhen

You cannot do that under 144 hour visa free transit because you will not be in a transit, but you can do the following:

Visitors from countries that have established diplomatic relations with China and are traveling in a tourist group organized by a travel agency registered in Hong Kong or Macau can travel to the nine mainland Chinese cities of the Pearl River Delta (PRD) region (Guangzhou, Shenzhen, Zhuhai, Foshan, Dongguan, Zhongshan, Jiangmen, Zhaoqing, and Huizhou) for up to six days without a visa.

To be eligible for this policy, the tour group must depart from Hong Kong or Macao.