I have grown golden zuccini before (same exact seeds last year - same package) and the same plant, until recently (I noticed it today), the zuccs were always BRIGHT yellow, from start to finish, completely. Today (cannot say when it started but very recently) I found green on young and medium aged fruits. I am pretty sure the medium age fruits did not have any green - ever, meaning what you see was yellow 2-3 days ago (if not yesterday).
I am 100% sure this is very recent - no green ever before from the same plant, same seeds etc.
All age fruits are showing green (not all but many). Never before.