I would do either SYD or GOR, not both in the 4 days you have. Way to much travel. You can easily spend 5 days in each city. Don't plan the trip around the PHs, just the activities. If you skip the GOR and just do MEL then it's barley possible to do SYD also, though I'd just do one. תפסת מרובה לא תפסת.