It is very complicated to advise you without your sample code. Unfortunately the RadMap does not contain any events which rise during zooming from one zoom level to another and which contain any data about current intermediate zoom level. Also it does not contain any properties like the 'scale' time.
I think you can use map shapes instead of drawing items when the zoom is changed. They are scaled smoothly when the zoom level is changed. For more information about map shapes please take a look at the following documentation topic:
All the best,
the Telerik team
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