I've seen this claim that phytic acid in plant foods blocks the zinc from being absorbed from animal foods like oysters.

It does look like a worrying graph. But I don't think that the claim is correct.

The graph is reproduced from this 1979 study. Studies aren't bad because they are old but they need to be in context of research since.

The key point is that it measures changes in plasma zinc, not absorption.
https://pubmed.ncbi.nlm.nih.gov/458251/ 

One way to look at this is the "cited by" articles on pubmed that shows you which studies have cited this one. Only 8 have since 1979 and no other studies seem to have used this method to measure zinc absorption. Suggests there is something up with it.

A clue is on the next page of the study (that no one shares). Feeding herring, a lower zinc food, with tortillas caused a drop in zinc in the blood below the starting level. White bread also caused a drop even though it is very low in phytic acid.

What is going on?

Soon after isotopes became used to accurately measure zinc absorption.

This 1980 study used both and found plasma zinc was unrelated to absorption. The lowest plasma zinc level was actually the meal where zinc waz absorbed the most.
https://pubmed.ncbi.nlm.nih.gov/7361691/ 

That study indicates that plasma zinc decreases after a meal and decreases more after a meal that is larger or that has more protein.

The plasma zinc went lower with bread, milk, and cheese than bread alone.

So a meal with tortillas and oysters is larger than oysters alone and would push plasma zinc down more than oysters alone despite the zinc being absorbed from the oysters pushing the plasma zinc up.

So the lower plasma zinc with tortillas is correct but is misleading.

But there is more.

The 1980 study measured the effects on zinc absorption from bread of adding small amounts of protein rich animal foods.
https://pubmed.ncbi.nlm.nih.gov/7361691/ 

Tables aren't as easy to read as graphs.

What it shows is that more zinc was absorbed from the wholemeal bread when the protein rich foods were added. This increased with increasing protein.

The protein seems to overcome the effects of the phytate.

So rather than the phytate in wholemeal bread blocking the absorption of zinc in animal foods it actually seems that the animal foods will help you absorb a bit more of the zinc from the bread.

Sadly, no one has ever again studied zinc in relation to oysters and tortillas. But we could assume that the same effect holds true.

Phytate definitely reduces the absorption of zinc from plant foods that contain zinc and phytate.

But I don't think we need to worry about the phytate blocking the absorption of zinc from meat or oysters.