bawal ang textspeak.
Anyway, getting past that.
Shred is a "style" of sorts. One that involves very technical playing. Neo-classical is a genre. The "formal" definition of neoclassical is contemporary music that is composed in the mould of what falls under the umbrella term of "classical" music (Baroque, Romantic, Classical etc). Composers include people like Bartok, Hindemith and Stravinsky. Pieces like Korngold Concerto are sometimes termed as "neo-classical" or "neo-romantic" because it is in the frame of "romantic" music.
But as i see in your context, you are reffering to Neoclassical METAL. That being said, this includes Yngwie, Chris Impeliterri and all those other neoclassical metal shredders out there. Hindi sila Neoclassical per se. Neoclassical METAL sila. Which is metal, inspired by classical music.
Not all shred is neoclassical. We have a lot of Jazz Fusion shred like Shawn lane or my personal favorite
Greg Howe:
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Meron din tayong Hard Rock Shredders like Buckethead. Meron din mga Straight up metal shredders like Zakk Wylde and Kiko Loureiro.
To sum it all up:
Shred is a style/technique
Neoclassical is a genre