Complex sentence: The name should be pronounced in either English, like the Italian name, but commonly mispronounced, which assumes that Shakespeare's spelling is genuinely Italian, is therefore a hyperforeignism: in Italian there is no name "Petruchio" so spelled.
Split into simpler sentences: The name should be pronounced in English, like the Italian name, but is commonly mispronounced. This pronunciation assumes that Shakespeare's spelling is genuinely Italian and is therefore a hyperforeignism: in Italian there is no name "Petruchio" so spelled.