What's the deference between zoing and spacing?
There are some similarities but it's something like this. Took one bit from SF in Zoning.
Zoning is when you are controlling a safe zone/space (in other fighting games, fireballs and projectiles are part of this to stop your opponent from crossing a line and condition them to do something else.) Ex: You can bait someone to do a jump-in at street fighter jumping over your slow fireball and he can net a free anti-air for someone trying to jump in. Zoning characters could take advantage of moves with long range or hurtbox along with strings, huge grab range. This could be considered keep-away too.
Zoning refers to fighting game tactics centered around keeping the opponent at a specific distance. http://streetfighter.wikia.com/wiki/Zoning
Many games are played differently regarding Zoning. DOA doesn't have natural jump ins like Street Fighter, so it's a different type of zoning but you could get some of that idea I guess? Spacing and Zoning is almost the same but Spacing could be considered a playstyle to hang back defensively and taking advantage of moves being out there.
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Spacing is when you are playing defensively with minimum aggressive offense to punish opponent in open space situations. Such as netting a CH in a specific situation and then doing a knockback move which sends them far across the screen and the opponent is forced to cool back from his/her pure offense/aggression. Whiff punishing moves out in the open, and can become best friends with the timer if the opponent is taking too long to make decisions to get in with the opponent who's spacing or playing keepout. If I have to come up with a Ying and Yang, this would be Ying and Yang would be the player who's pure rushdown or aggressor that's really good up close. People take spacing negatively for whatever reason, but it's a genuine tactic because you are playing the game without taking damage and the goal is to prevent health loss and dropping your opponents health.
In a way they are kind of the same somewhat, if there was a short answer, both of those are not in your face so there's that.