Themeing cck input form with a zen subtheme

I've struggled with this for days now, about to freak out. Please can somebody help??
Using drupal 6.9, zen 6.x 1.0

Starting over, this is the current state:
1. Created a content type called 'medprac' (machine readable name).

1. Created a zen subtheme called 'zentagit'

2. Altered template.php in zentagit theme folder like this':
   Copied the 'theme_node_form' function from the core node directory file node.pages.inc and pasted it in the zentagit theme's template.php file.
   Renamed the function to read 'zentagit_node_form'

3. Using 'devel' module - the input form continues to use 'theme_node_form'; (the function 'zentagit_node_form' is listed in the candidate functions list).

I've cleaned the theming registry.
This is the first time I'm using the devel module so I'm not too sure how to interpret/use the info.
I've tried other ways to do this. I've tried with non-zen themes.

Any advice please?