rupa/z ? reverse-engineered prompt

Build me a small shell tool that helps me jump to folders I use a lot without typing long paths.

I want it to work in bash and zsh, and I should be able to source one script in my shell startup file and then just type a short command like z. It should remember where I go over time, learn which directories I use most often, and take me to the best matching folder when I give it one or more search words. The matching should feel smart, so recently used folders count more, but folders I use a lot still matter too.

Please include a few helpful options for listing matches, showing the best match without changing directories, matching only by recent use or rank, limiting matches to the current folder, and removing the current folder from the saved data. It should store its data in a file in my home directory by default, and let me override that with an environment setting. If you need to check current shell behavior or docs, look them up online.