About zoom on the AviSynth preview screen.

[Selur]

short: No
long:
In the lower right corner in the Vapoursynth Preview (vsViewer) Window you can select:

• Fit to frame: this way the preview will be resized to the window size (using the resizer next to it)
  
• Fixed ratio: this way you can select a zoom ratio (using 'ctrl+mouse wheel' you can change this value too) to zoom in
  
• No zoom: this way no zoom will be performed
  

In Avisynth Preview (avsViewer) nothing like this exists. Patches are welcomed. (https://github.com/Selur/avsViewer)

Cu Selur