I think that you will never see all zeros because one VLF is always in use. What you need to see is 2 near the beginning and zeros at the end. We can't shrink a file from the middle, only by cutting off the end.

Also, the word is "extents", not "extends".

Also, DBCC LOGINFO shows one row per VLF, not per extent [thank goodness, that would be horrible]