Add the cities that have to be on the call. Add Sydney to Miami and London and watch the good window disappear.
5 clean hours. Earliest is Miami 8:00am, London 1:00pm.
That is what I look at when I am booking across timezones. Add cities and watch the window narrow.
Miami, London and Tokyo do not share a working day, and no clever trick makes them. Once you accept that, scheduling gets easier, because the job stops being arithmetic and starts being a decision about who gets inconvenienced.
Everyone can convert timezones. What takes judgment is the case with no answer. Add Sydney to Miami and London and the clean window disappears. At that point people usually keep hunting for a slot that does not exist, and the meeting slips a week.
So I book the least bad hour and say out loud whose evening it is. "This is 9pm for Tom" belongs in the invite, not discovered on the call. Then I rotate it, because the same person eating the bad slot every month is how a standing meeting quietly dies.
I also stopped asking three people to compare calendars. It is faster to propose one time with the tradeoff written down and let someone object.