Off topic:How to change file extension of multiple files

Question

[fiona.newberry]

I have 4 directories and within those I have 10 subdirectories with 20 files in each subdirectory. I have stupidly named them .fq.qz instead of .fq.gz

I am trying to use find/exec to change the file extension to gz instead of qz.

Not quite sure how to go about it though