JDK-8241825 decoupled UseCompressedClassPointers and UseCompressedOops, and introduced COMPRESSED_CLASS_POINTERS_DEPENDS_ON_COMPRESSED_OOPS that platforms can set to say if their generated code is ready for this decoupling.

Zero defaults to "true" for that flag, meaning the flags are still coupled. But there is not actual coupling: Zero delegates all this work to VM code, which handles everything correctly.

This makes at least one test fail with Zero:

runtime/CompressedOops/CompressedClassPointers.java
java.lang.RuntimeException: 'Narrow klass base: 0x0000000000000000' missing from stdout/stderr