Since I don't need new credit for the time being, I've been experimenting a little bit. I have a dirty file with a BK and my EX score has been at 702 for the last few months (untill today).
Two months ago: AZEO in effect, total utilization 2%, individual card utilization 8%, score 702.
One month ago: AZEO in effect, total utilization 4%, individual card utilization 15%, score 702.
Today: AZEO broken (all balances zero), total utilization 0%, individual card utilization 0%, score 684.
So I lost 18 points because of the all-zero penalty.
In 3 days another card will report in with a balance and I will be back to AZEO with total utilization 1% and individual card utilization <5%. Curious to see how much the score bounces back by. Will report back.
More than likely you'll be right back where you started before @AllZero . LOL!!!!!! Sorry just had to.
What's funny is I performed the same basic test and saw a pretty significant drop in my scores when I hit All Zero; the funny part is when I went to AZET (All Zero Except Two), my scores rebounded to where they'd started, plus one. Not sure where that extra point came from, but hey, I'll take it. 
@FireMedic1 wrote:More than likely you'll be right back where you started before @AllZero . LOL!!!!!! Sorry just had to.
Oh, I have little doubt about that. But I'm a data analysis nerd and I like to conduct my own experiments!
@Focker69 wrote:
Which version of Fico was this for? Fico 8?
I'm not sure whom you were responding to, but in my case, the comments I made above were relative to all 28 scores.
@Sub16610 wrote:
@NYC_FellaCurios to know the result of your finding "In 3 days another card will report in with a balance and I will be back to AZEO with total utilization 1% and individual card utilization <5%. Curious to see how much the score bounces back by. Will report back."
Unfortunately we will now have to wait until October 7. I was counting on my Apple card to report a balance 2 days ago but an unexpected refund wiped out my balance on the statement closing date. My Barclays Aviator Red card will report on the 6th so I will charge something on that today to get out of all-zero purgatory.
I temporarily (and intentionally) broke AZEO as I wanted to change the "one" card on which I was carrying a balance. So I was at all-zero on September 27 which dropped my FICO 8 scores by ~18 points as expected. I expected a balance to be reported on my new "one" card on October 5 causing my scores to bounce back.
But for some reason, only EQ is showing the updated balance and the resultant score increase, while EX and TU are still showing last month's zero balance so the scores are still artificially depressed. Is there a way to force an update? I would like all 3 scores to be optimized before I apply for new credit.
Following up on that thought, would the score reduction (702 to 684) have an impact on credit decisions, or would the scores be considered to be in the same group?