Sentence taken from this question：
"Yeah, right. I , too, was thinking that it would (probably) be just as good to keep it as to throw it away." (translation thanks to l'electeur)
I'm more interested in the part in bold. I'm very confused by this double conditional construction AならBたらどうかしら. Literally I'd translate this as "If you were to end up throwing it away, I wonder how it would be if you kept hold of it". Whilst my translation is clearly gibberish, I can see how it might turn into the good translation, but only because I've seen the good translation. I certainly couldn't have worked that out for myself.
Could you provide some clarification (perhaps with simpler examples) on how to parse this sentence and on how the grammar works here?