Looks pretty clear cut;  tacking in the zone causing yellow to change coarse.

10 or 13

Charal clearly violated 18.3. As a side note, sailing close quarters with those foils looks pretty scary. The AC70s are going to be much worse in that regard. 

This would be ok under the match racing rules.

It's very hard to appreciate the real situation on the pictures.
What I see is the black boat port tacked not keeping clear of yellow boat starboard tacked.
Rule 13 would apply when black passes head to wind.
Rule 18 does not apply between boats on different tack.

Anthony, can you clearly tell that the yellow boat had to sail above close-hauled to avoid the black boat? It's hard to tell from the picture but the yellow boat's jib doesn't seem to be luffing. If that's the case, it's a bold move but I think it's legal. Also, the scale is hard to tell because of the telephoto foreshortening, so without a different set of pictures it may not be nearly as close as it looks.

Jim, there is no rule that says you can't tack in the zone and cause another boat to change course. 18.3 says that you can't cause a boat that has been on starboard tack since entering the zone to sail above close-hauled.

While a quick look at the pictures makes this seems pretty clear-cut, I agree with others that it is not that clear. It is not obvious that the yellow boat is sailing above close-hauled, although that is most likely the case. It is also not possible to tell if the yellow boat has been on starboard tack since entering the zone, so I can't tell if 18.3 applies or not.

Lance,
I can see that two pictures may not be enough to resolve things with 100% certainty. I don't, for example, don't know that yellow was on starboard since before entering the zone. I agree was too certain in my statement. 
My reason for believing that this is a violation requires a little extrapolation. In the first photo, yellow may have the leach of her headsail a little open (perhaps car back a little), but generally seems trimmed to close-hauled with the jib trimmed inside the spreaders all the way up the leach. Looking at the boats on the lay line behind, they do not seem to be reaching down. They appear to be close hauled and at almost the same angle as yellow. I don't think you could turn this beast down without easing the jib, as green is already doing in photo one. So, I'm going to say I think yellow is on close-hauled course in photo 1.
The second picture does not show the mark, I'm assuming this happened in very close succession and the mark is just outside to the right of the photo. I don't think yellow's jib can be seen clearly enough, though, through the portion you can see, there is no obvious luffing. You can still see the boats behind yellow who are on close-hauled course. Black is matching that angle and is trimmed for close hauled. Yellow does appear to have turned up from its previous course significantly and, based on the evidence cited above, I believe that she has had to go above close-hauled.
Were I adjudicating this, I would conclude that yellow had to sail above close hauled, especially given the appendages. 
But, thanks for pushing the conversation. I will stipulate telephoto lenses can be deceptive  and one camera angle is not a perfect data set. Were this happening in dinghies with my high-school sailors, I would tell black that they should spin. 

There is not enough information in the two photos alone to determine all the relevant facts in this situation.  As mentioned, the camera has foreshortened the distances and there is no way to tell the separation between the boats.  It appears as though the green boat may have just completed a tack onto starboard in the first photo.  If Yellow had tacked inside the zone, then it is irrelevant whether she had to sail above close-hauled or up to or beyond head to wind after black had completed her tack.  If this was the only information available to a protest committee, the protest would be dismissed.

From the angles of the boats before and after I would think RRS 13 (tacking) has been breached by black and possibly also RRS 10 (port/starboard). My analysis is based on reconstructing the positions between the two photos. In 23.jpg for yellow to have got to its angle which was a substantial change of course while black appears to have likely not quite got to close hauled a breach of RRS13 appears to have been quite likely, but without an overhead or other evidence to show the distances between boats it is not possible. Maybe yellow's position in 23.jpg s is explained by yellow having to pull out of the rounding because she otherwise risked a late overlap with green who had left enough room for black to get inside her and to the mark without forcing green above close hauled (RRS 16). 
A belated Happy New Year to all from Sydney, Australia where some races were cancelled because of poor visibililty as a result of thick smoke from bushfires.  
See 
https://cdn.newsapi.com.au/image/v1/da9b457ac0003a56be91c96ca8873ea2?width=650
 for photo of barely visible Sydney Harbour bridge.

Black boat may have broken Rule 10 and 13. Rule 18 does not apply for boats on opposite tacks on a beat to winward.

Great photos and great discussion all of which proves how carefully we need to look at phots and videos in the protest room..
And also a belated Happy New Year from Lake Macquarie 100+  Km north of Sydney Aus

Another possibility  (yes I know) is that Y had just tracked onto starboard and was giving room to keep clear