ZBrushCentral

Importing obj file , hidden lines

Hi I am new to z-brush so maybe this is a noobish question , however I could not find the answer in google so here I am. I exported a google sketchup model to an obj file. In the first image you can see the model , notice the lines in the middle. After I import it in z-brush the lines are hidden or maybe not being exported at all I am not sure. See image 2. So anyone know how can I get the lines to be visible in zbrush after the export from G-sketchup ?

img 1 - google sketchup https://s14.postimg.io/528ypjmhd/before.png
img 2 - Z-brush https://s10.postimg.io/3u92edv49/after.png