Replicating R unz function in Power Query. Based on http://sql10.blogspot.co.uk/2016/06/reading-zip-files-in-powerquery-m.html

Unz.m

(binaryZip,fileName) =>
let
//shorthand
    UInt32 = BinaryFormat.ByteOrder(BinaryFormat.UnsignedInteger32,ByteOrder.LittleEndian),
    UInt16 = BinaryFormat.ByteOrder(BinaryFormat.UnsignedInteger16,ByteOrder.LittleEndian),
//ZIP file header fixed size structure
    Header = BinaryFormat.Record([
	    	MiscHeader 	 	= BinaryFormat.Binary(14),
                CompressedSize   	= UInt32,
                UncompressedSize 	= UInt32,
                FileNameLen      	= UInt16,
                ExtraFieldLen 	 	= UInt16]),
//ZIP file header dynamic size structure
    FileData = (h)=> BinaryFormat.Record([
                FileName         	= BinaryFormat.Text(h[FileNameLen]),
                ExtraField       	= BinaryFormat.Text(h[ExtraFieldLen]),
                UncompressedData 	= BinaryFormat.Transform(
	    		BinaryFormat.Binary(h[CompressedSize]),
	    			(x) =>  try 
	    				Binary.Buffer(Binary.Decompress(x, Compression.Deflate)) 
	    				otherwise null)]),
//Parsing the binary in search for PKZIP header signature
    ZipIterator = BinaryFormat.Choice(UInt32, (signature) => if signature <> 0x04034B50 
                                            then BinaryFormat.Record([FileName=null])
                                            else BinaryFormat.Choice(Header,(z)=>FileData(z))),
    ZipFormat = BinaryFormat.List(ZipIterator),
    out = List.Select(ZipFormat(binaryZip), each _[FileName]=fileName)
in
    out{0}[UncompressedData]