The ZapQuake tactic has obtained big success as it allowed (and still does) to get also 3 stars in war, farming, and climbing on Clash of Clans.
Mainly, this strategy allowes to take advantage of the combo Lightning Spell + Earthquake Spell on Air Defences to then destroy the Village using Air Troops, that will have, at this point, clear field with only half of the most powerful defences against them.
By using 2 Lightning Spells and 1 Earthquake Spell it will be possible to destroy 1 Air Defence of maximum level (of the respective Hall). So, by carrying 4 Lightning Spells and 2 Earthquake Spells we can halve the Air Defence from 4 to 2.
Manu expert players also use a kill team, based on Barbarian King + Archer Queen to destroy the third Air Defense ( in the case in which it is more external and easy to reach). At this point we will even have only 1 Air Defence left against our army!
It’s not all: some players, especially those with low level Halls, usually position all 4 Air Defences at the center of the Village. Needless to say, 4 Lightning Spells and 4 Earthquake Spells can destroy all 4 of them and have clear field completely!
At this point it will be sufficient to position Dragons, Baby Dragons or Ballons on the side where there are the other two (or one) Air Defences to destroy them in a blink of an eye and ensure 3 stars easily.
Not to mention that the Eathquake Spell used on the Air Defence can lower down the hitpoints of the structures next to it, making their demolition even easier: we are talking about Eagle Artillery, Inferno Tower or X-Bow that have a remarkable quantity of hitpoints.