Advanced Command-Line Editing

Today I passed my 117-201 exam and now I play a little bit with the Vi key bindings on Zsh.
In Bash you can set them with set -o vi, and in Zsh you can set them additionally with setopt vi.

I want to get to the point of command line editing above the basic
tab complete and history browsing, searching and minor corrections.
So I start witch a little example:

I want to rename a file with the following naming scheme:

someID_filename.txt to filename.txt

After my fulminant efficient Vim key combination for table editing, Efficient table-editing
I challenge everybody to find the shortest key combination to fulfill this task.

I start with an self-deprating solution: First I type: mv someID_filname.txt

Now the count begins:

<Space><Esc>T_y$$p<Enter>

This makes a total of 9 characters which i have to store in my brain. As I want to have my head free for more complicated tasks, of course this has to be optimized dramatically :)

Have fun.