Megamorph is a variant of the morph ability. “Megamorph [cost]” means “You may cast this card as a 2/2 face-down creature with no text, no name, no subtypes, and no mana cost by paying {3} rather than paying its mana cost” and “As this permanent is turned face up, put a +1/+1 counter on it if its megamorph cost was paid to turn it face up.” A megamorph cost is a morph cost.
July 13, 2013 · Magic 2014
If a creature has multiple instances of amplify, each one works separately.
June 17, 2011 · Commander 2011
If a creature has multiple instances of provoke, each triggers separately.
February 1, 2010 · Worldwake
If a spell has multiple instances of storm, each triggers separately.