The phrase "in a zone" typically indicates that a person is fully immersed in a task or activity, and it can be helpful to have synonyms to convey this idea in different contexts. Some possible alternatives might include "in the groove," "locked in," "dialed in," "in the flow," "in the moment," or "in the thick of it." Each of these terms emphasizes a slightly different aspect of being intensely focused, whether it's a sense of being connected to a certain rhythm or simply experiencing deep concentration. Regardless of the specific wording, all of these phrases convey a sense of being deeply engaged in the present moment.