China embassy in Bangladesh do issue Z visa, and the requirements are:
1. Valid passport (at least six months before expiration) with blank visa pages and copy of the first three pages;
2. TYPED Visa Application Form with one passport photo.
3. Applicants who have never been to China before should submit in person.
4. Original Employment License for Foreigners issued by Ministry of Human Resources and Social Security of China and copy
5. Original Visa Notice Form issued by authorized departments of Chinese Government
6. Physical Examination Report from local public hospitals and copy.
A z visa is just valid for 3 month, and you have to apply for a residence permit within 30 days of your entry in China. The validity of the residence permit is 1 year, 2 years..., according to your employment contract with your Chinese employer.