4. The fourth case is where each of the two vowels bears the stress:
Así, ante nosotros pasa en ilusión (12)
What happens here is that one of the two stresses becomes subordinate to the other, the stress being wholly assumed by the more dominant of the two.
Where three or more vowels unite in a synalepha, two things must be borne in mind: (1) Stress-shift is not harsh to the Spanish ear, and is always permissible, if more than two vowels are involved. This is Espronceda's justification in the following:
Si se murió, a lo hecho, pecho (8)
Necesito ahora dinero (8)
Su pecho ahogado (5)
(2) The vowels of three words may not combine if the middle word is y, e, he, o, or u. Examples:
¡Pues no ha hecho mal disparate! (8)
Que conduce a esta mansión (8)