GeometryComparator

viewPort.getQueue().setGeometryComparator(Bucket.Transparent, new TransparentComparator() {
            @Override
            public int compare(Geometry o1, Geometry o2) {
                Entity e1 = o1.getUserData("Entity");
                Entity e2 = o2.getUserData("Entity");
                boolean sharesTile = (e1 != null && e2 != null) ? e1.getLocation().equals(e2.getLocation()) : false;
                if(sharesTile) {
                    int z1 = e1 != null ? e1.getZOrder() : 0;
                    int z2 = e2 != null ? e2.getZOrder() : 0;
                    if(z1 == 0 && z2 == 0) {
                        return super.compare(o1, o2);
                    }
                    return z1 - z2;
                }
                return super.compare(o1, o2);
            }
        });