I try to out put Zdepth ,some serid quesiotn troubles me

I tried out put the z depth in different conditions,
It seems when Ztest is Equal,LEuqal,GEuqal and always, the z Buffer was not written
Even if i forced by ZWrite On,
So anybody could explain more?

Has anybody tried the same thing?
I use fixed pipeline

any guru?

Open, sesame! :frowning: