im doing a quite large character and want to retopologize but scaling has some limits and using zoom pixelate which hard to see the rig, any solution to this?
The only fairly decent solution seems to be to hide the parts of the model you’re not working on. But I’m sure you already knew that one.
There’s also the ‘scale’ technique, but try as I might, I’ve never managed to get that working. 
I’m really just chiming in to let it be know that I hope Pixologic are working on some methods of improving this zoom limitation.
Sorry I don’t have any helpful tips for you. 
i hope this will resolve soon quite frustrating
What works for me, though this is just a workaround. Is while your in “edit topology mode”.
- " hit “a” to preview the mesh.
- Markee select part of your mesh, say a hand for instance.
- Then press “f” to center your hand.
- Then alt click to zoom up close, rotate now as needed for best view.
- Cancel preview mode by clicking “a”
- Your now in “edit topology” mode.
- Only click within your “hand” to edit topology,not outside to say rotate it or it will zoom back to the default view.
Each time you need to re edit, click “a” to preview, select part for editing, hit “f” to center view, then alt click to zoom as far as you can. Then click “a” to cancel preview which takes you into edit topology mode.
But remember not to click outside your model or it will zoom back.
Hope this helps you all. 
can you explain whats in the number 2? : “2. Markee select part of your mesh, say a hand for instance.” under edit topology?
I believe OP meant “Shift+Ctrl and LMB drag” to select the portion of the mesh to visible.
Example is avaialb eat following link:
http://www.zbrush.info/docs/index.php/Hiding_and_Showing_Model_Parts
Yes, ahem… That is what I meant. Use shift +ctrl + LMB to select a part of your mesh that you want to concentrate on.