So here's my question, if I were to use a card like Teferi's Protection and have all of my permanents phase out, and someone else cast Balance, does my field count as zero for everything since they've phased out, or since they technically didn't change locations do they still count somehow? To put it clearer, if I had ten lands on the field before protection and my opponents had 20 each, would they have to reduce to 10 or zero after Balance was played?
Phased out permanents are treated as though they don't exist (see the reminder text of TP). So Balance cannot see them, which means, you are treated as having zero lands and zero creatures. Thus all other players will go down to zero lands and zero creatures when Balance resolves.