I use the model number as the image name on my website too, if you want to go that route you should consider splitting the images folder into sub folder, in my case I have a different folder for each brand.
Second you can download a utility tool that will do bulk rename for you, I am using bulk rename utility its free and does wonder.
Or you can change the way Zen Cart handle the image name. I am using image handler so I changed the additional image reference from (-) to (_).



