This keyin script was posted to v8.general by Truels Wissneth and allows you to zoom in on elements that are in a selection set. 

set displayset on;selview 1;displayset set selection;fit all;point ab;displayset clear;update view extended
Stick it on a function key and you're all set!

If you prefer to have the elements released from the selection set after the zoom operation, simple append choose none on the end of the key-in string.

communities.bentley.com/.../0068.462.mp4

Tip:
In sheet models, the sheet border is disturbing for this command and should first be switched off: Turn off display of sheet boundary

Alternatively, the switching on and off of the sheet boundary could be integrated to the key-in, so you do not need to care for the switching of the sheet boundary: sheet boundary off;set displayset on;selview 1;displayset set selection;fit all;point ab;displayset clear;update view extended;sheet boundary on

Related Tip:
Fit Selected Elements To View