Well, if we’re going by Italian pronunciation, seeing as Giacomo is an Italian name, ‘ce’ is a hard sound, corresponding to English’s ‘che’. So yes, Mar-CHEL-lo DI JAH-como
‘Gi’ in Italian is the English ‘J’ as the Italian alphabet lacks the J letter (or K, W, X, Y). Pronounced, try making the ‘Jah’ sound in ‘Java’, only exhale through the J instead of it being a hard consonant where you cut off your exhale. It’s a softer J than the English J, but it’s not the soft J that mimics an H in Spanish.
The ‘a’ in Italian is short, so ‘Gia’ is ‘Jah’, not ‘Jae’
…which is almost perfect. In Italian, you pronounce every letter…so you DO pronounce the ‘i’ in Giacomo, (it’s a long e in English) it’s just unstressed and blends in with the ‘J’ sound.
TLDR; Marcello DiGiacomo would be pronounced as Mar-CHEL-lo Di JAH-como