Add & subtract rational expressions: factored denominators

Problem

Add the following rational expressions.
Keep the denominator in your answer in its factored form.
start fraction, 3, z, start superscript, 3, end superscript, divided by, left parenthesis, 9, z, plus, 2, right parenthesis, left parenthesis, z, minus, 4, right parenthesis, end fraction, plus, start fraction, 7, divided by, left parenthesis, 3, z, plus, 1, right parenthesis, left parenthesis, z, minus, 4, right parenthesis, end fraction, equals
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