Many (all?) ZGC related jtreg tests do not work when the JDK is built with address sanitizer asan enabled (configure flag --enable-asan).
My test environment is SUSE Linux x86_64 , opt binaries were used.
Example jtreg test gc/z/TestAllocateHeapAt :

----------System.err:(35/1917)----------
 stdout: [[0.014s][info][gc,init] Initializing The Z Garbage Collector
[0.014s][info][gc,init] Version: 25.0.0.1-internal-adhoc.user.jdk (release)
[0.014s][info][gc,init] NUMA Support: Enabled
[0.014s][info][gc,init] NUMA Nodes: 4
[0.014s][info][gc,init] CPUs: 88 total, 88 available
[0.014s][info][gc,init] Memory: 64242M
[0.014s][info][gc,init] Large Page Support: Disabled
[0.015s][info][gc,init] Address Space Size: unlimited
[0.351s][error][gc ] Failed to reserve 32M address space for Java heap
[0.354s][info ][gc,init] Heap Backing File: ./java_heap.28264
[0.354s][info ][gc,init] Heap Backing Filesystem: other (0x6969)
[0.356s][info ][gc,init] GC Workers for Old Generation: 1 (dynamic)
[0.356s][info ][gc,init] GC Workers for Young Generation: 1 (dynamic)
[0.357s][info ][gc,init] Runtime Workers: 1
[0.357s][info ][gc ] Using The Z Garbage Collector
Error occurred during initialization of VM
Failed to reserve 32M address space for Java heap


Also 'java -version' fails with ZGC :

./images/jdk/bin/java -XX:+UseZGC -version
[0.032s][error][gc] Failed to reserve 16062M address space for Java heap
Error occurred during initialization of VM
Failed to reserve 16062M address space for Java heap
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.