If you have two previous China visas in the past year, it is a little easy for you to get a multiple entry L visa to China. Because you can't prove that you need multiple-entry visa of China, it is hard for you to get the multiple-entry visa, anyhow, try to apply for mutliple-entry visa, the worst thing is that you get a single-entry visa.

You can have a try in this way, when you fill the travel itineray on the visa applcation form, you can write that you will visit Mainland China - Hong Kong - Mainland China -Macau -Mainland, then the visa office will know that you need multiple-entry visa.