Left and Right region is not showing on ZEN sub theme
I finally found the solution for this problem. That is the put 'zen' folder under the same location of the sub-theme folder. Actually, the site I've been working on is a multi site setup and there is also an entity there that is also using zen as it's theme. I thought putting just my sub-theme is enough since the site still recognized the main theme, which is Zen.

The reason why the two region of the theme I uploaded is not being recognized, is because it's info file is not being read properly. The info file that is being read by the site is found, on the other zen sub-theme I mentioned above.