public NumberExpression<Double> z() {
        if (z == null) {
            z = Expressions.numberOperation(Double.class, SpatialOps.Z, mixin);
        }
        return z;
    }
The z-coordinate value for this Point, if it has one. Returns NIL otherwise.

@return z-coordinate
querydsl-spatial/src/main/java/com/querydsl/spatial/locationtech/jts/JTSPointExpression.java