Flattening directory and renaming files incrementally (MacOS)

Looking to flatten the directory (with duplicate child file names) while renaming all files, keeping duplicates OR appending all file names with an incrementing number (incrementing # + name would be preferred but not required). This would need to work on MacOS - updated bash to 5.0.11. This is part of a multi-step process (unzipping recursively, flattening while keeping duplicates, pdftotxt, grep for strings > txt file) but this is the part I can't get figured out after a few hours of searching/testing.

Example:

Any help?