Pilou,
I noticed when you export obj from MOI in triangle and quads, it first create triangled model, than merge triangles that can be merged with easy (using some algorithms) and make it in seconds (may be I'm wrong Michael know better)). The same thing can make Zbrush in seconds but still model will have triangles.. If it will be so easy Michael made the option export in quads)

Michael, just noticed that when I subdivide with smooth function model that was exported from moi with quads+triangles, it make all polygons quad (white).
And when I run simple subdivide it not creates quads (red). What is the trick)?

And it's peaty that this method can not be used to convert all to quads because it distort a bit geometry when smoothing. It very noticeable on sharp edges, on smooth surfaces works good.