I'm not sure I understand the question. Are you saying you want to keep
the circles a constant size while zooming?
This might be relevant:
http://www.jasondavies.com/poincare-disc/
I used SVG's transform for zooming, while changing the stroke-width to
keep it a constant width at different scales. The code is here:
http://www.jasondavies.com/poincare-disc/poincare-disc.js
Likewise, to keep the circles a constant size you need to invert the
transformation on the radius (and potentially the stroke-width).
--
Jason Davies, http://www.jasondavies.com/