OK, firstly sorry if my writing is bit confusing. i'll try to clear it up with this explanation.

My first example which updates the newzip column, is actually to demonstrate the method widely suggested to follow when you add a new column to a very large table. That's just an example, and i first used that method to do the update on my own table called [LargeTable] and that's the one took 20+ hours. And i haven't posted it in the article because the provided example (with NewZip column) is good enough to understand what it does.

But for the solution i am suggesting, i have given the exact code i ran on my table [LargeTable].

Hope this clears the confusion.