AFAIK no more Z visas 1 year multiple no time limit entry since the Olympics.

Most you can get now is L visa 6 months, multiple, with 30 day stay limit. This should apply to biz visas with invitation from Chinese company. Might be worth to contact CTS in HK to check if they are more flexible now.

http://www.ctshk.com/english/useful/chinesevisa.htm