RETLW 0 and RETURN command on PIC10F222 microcontroller
Firstly, you should really add comments to your assembler code. It is not clear what sections are subroutines and what sections are loops. There are also a lot of jumps with similar names which makes tracking what is going on quite difficult. It might be clear to you right now, but in a few weeks time when you have to edit it, you'll thank yourself for adding comments.

To answer your question, the retlw 0 will just put zero into the w register during the return. Whether this has any effect on the rest of your program depends on what the calling code expects in the w register. It is common for calling code to expect the w register will be modified by a subroutine, in which case you should save the contents before you issue the call if it contains something important. But this is just a convention. As you are working in assembler you can decide to save the context inside the functions instead if you prefer this (it also means you can make functions re-entrant, though on a PIC10 that is rather pointless as the return address stack is so small).

So you really just need to step through your code and see if anything following the subroutine call expects something in the w register. From briefling looking at the code, it does not look like this is the case, in which case there is no effect from the substitution.