I found this bit of code on the Microsoft Community page that should work in the Field Calculator using VBScript:
Assuming there is no space character in the data:
Replace( LTRIM(Replace( fieldName, "0", " ")), " ", "0")
The part in bold replace all zeros by spaces, and then, left-trim that result, ie, remove starting spaces. The external Replace replaces the spaces left in the string to their initial 0 character.
Used to be that we could simply multiply the text as a number by 1
000012 x 1 = 12
Trying to find out what this might look like today from within ArcPro is up to you
This thread popped up in my activity log today. You can do the same calculation in pro as I described above or use the int() function :
I guess the int() function would have worked originally too....