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eml(z, eml(x, 1))
= e^z - ln(eml(x, 1))
= e^z - ln(e^x)
= e^z - x
and the claim is that, after it's expanded, z will be such that this whole thing is equal to -x. but with some algebra, this is happening only if e^z = 0,
and there is no complex number z that satisfies this equation. indeed if we laboriously expand the given formula for z (the left branch of the tree), we see that it goes through ln(0), and compound expressions.