Compressing wbfs to gcz

Hi everyone. I've recently discovered that dolphin can compress Wii and GameCube images into .gcz format and it compresses most games fairly well. However whenever i compress a .wbfs image into .gcz they always come up corrupted and dolphin wont run them.

Is it because wbfs image files cant be compressed? And if thats the case would it be better to convert wbfs to iso then compress it to gcz?