The most common thing I've seen elsewhere in Cesium is `new Cartesian3()` (193 occurrences).  I've been doing `new Cartesian3(0.0, 0.0, 0.0)` (37 occurrences) because it's slightly more performant and arguably clearer.  I'm fine with switching to `new Cartesian3()` though.  I'm not a fan of `Cartesian3.ZERO.clone()` (9 occurrences).