Is there any chance that the 濁音 ザズゼゾ could be pronounced differently when they are in 外来語? It seems to me that when any of these kana's is part of the loanword from the English language they are often read more like the English sound rather than what I have expected as in the Japanese language. I can't say anything about those derived from other foreign language though. Perhaps the position of the kana in the word has some bearing on the pronunciation. So far I haven’t heard of any difference between じ and ジ with non-loanwords and loanwords.
For example:
ざ: 銀座 雑誌 諺
ザ: ブレザー ザ(the)
ぜ:ぜひ 大勢 風邪 午前 自然
ゼ:ガゼ
ず: ずっと 図示
ズ:メンズ キッズ サイズ コミカライ ズーム
ぞ: 存知 象
ゾ: ゾーン ゾンビ
For example:
ざ: 銀座 雑誌 諺
ザ: ブレザー ザ(the)
ぜ:ぜひ 大勢 風邪 午前 自然
ゼ:ガゼ
ず: ずっと 図示
ズ:メンズ キッズ サイズ コミカライ ズーム
ぞ: 存知 象
ゾ: ゾーン ゾンビ