Well, ZDM had different operating methods. In the physical online method what ZDM does is the following;
provisions target as a Data Guard standby of source sync via redo and then switches over.
Physical online = near-zero downtime.
For the near-zero downtime, it also supports logical online method (GoldenGate...)
So, also, logical online = near-zero downtime
You should follow ->
https://docs.oracle.com/en/database/oracle/zero-downtime-migration/21.5/zdmug/so just go through ->
Setting Up Zero Downtime Migration Software
Preparing for Oracle Database Migration
Physical Migration Workflow
Migrating Your Database with Zero Downtime Migration