hubieran temblado
-they/you had shaken
Antecopréterito de subjuntivo para el sujeto ellos/ellas/ustedes del verbo temblar.

temblar

Si hubiéramos podido entrar a la arena del desarrollo socialista tras la victoria de la revolución en Europa, a nuestra burguesía le hubieran temblado las piernas y hubiera sido muy simple enfrentarse a ella.
Indeed, had we been able to enter the arena of socialist development after the victory of the revolution in Europe, our bourgeoisie would have quaked in its boots and it would have been very simple to deal with it.
Palabra del día
la fiesta de traje