user100856: I am trying to research hash functions and I want to be able to use bitcoin's mining outputs as hashes. I am curious about where the actual hex value of the data that generates that hash with a lot of zeroes is. So, this is what I want: the 80 byte input that gives a 32 bit output with a lot of zeros from sha256(sha256(x)).

user71774: 
I am curious about where the actual hex value of the data that generates that hash with a lot of zeroes is.

It is a composite of values from the block - in brief, it is the concatenated binary (represented here in hex notation) little endian value of each of the fields:
version + previous_block_hash + merkle_root_hash + time + bits + nonce
of the block that is being mined.
These are contained in the "block header".
You have examples of Python code here: https://en.bitcoin.it/wiki/Block_hashing_algorithm , for example for block 125552:
>>> import hashlib
>>> header_hex = ("01000000" +
 "81cd02ab7e569e8bcd9317e2fe99f2de44d49ab2b8851ba4a308000000000000" +
 "e320b6c2fffc8d750423db8b1eb942ae710e951ed797f7affc8892b0f1fc122b" +
 "c7f5d74d" +
 "f2b9441a" +
 "42a14695")
>>> header_bin = header_hex.decode('hex')
>>> hash = hashlib.sha256(hashlib.sha256(header_bin).digest()).digest()
>>> hash.encode('hex_codec')
'1dbd981fe6985776b644b173a4d0385ddc1aa2a829688d1e0000000000000000'
>>> hash[::-1].encode('hex_codec')
'00000000000000001e8d6829a8a21adc5d38d0a473b144b6765798e61f98bd1d'

Note that the value is reversed at the last step in order to be represented in the big-endian format that we humans are used to.

So, this is what I want: the 80 byte input that gives a 32 bit output with a lot of zeros from sha256(sha256(x)).

You can check these 6 values for every block mined using any one of the many online block explorers available: for example here for the particular block of the previous example: https://blockexplorer.com/block/00000000000000001e8d6829a8a21adc5d38d0a473b144b6765798e61f98bd1d (you'll only have to convert the human time to unix time being careful with the time zone).
Here is a quick link to download blocks' headers in binary form (until May 2018) and start playing with real values. You can convert it to .csv if needed.

100856: <p>I am trying to research hash functions and I want to be able to use bitcoin's mining outputs as hashes. I am curious about where the actual hex value of the data that generates that hash with a lot of zeroes is. So, this is what I want: the 80 byte input that gives a 32 bit output with a lot of zeros from sha256(sha256(x)).</p>
 71774: <blockquote>
  <p>I am curious about where the actual hex value of the data that generates that hash with a lot of zeroes is.</p>
</blockquote>

<p>It is a <a href="https://en.bitcoin.it/wiki/Block_hashing_algorithm" rel="nofollow noreferrer">composite of values from the block</a> - in brief, it is the concatenated <strong>binary</strong> (represented here in hex notation) <strong>little endian</strong> value of each of the fields:</p>

<p><strong><code>version + previous_block_hash + merkle_root_hash + time + bits + nonce</code></strong></p>

<p>of the block that is being mined.</p>

<p>These are contained in the "block header".</p>

<p>You have examples of Python code here: <a href="https://en.bitcoin.it/wiki/Block_hashing_algorithm" rel="nofollow noreferrer">https://en.bitcoin.it/wiki/Block_hashing_algorithm</a> , for example for <a href="https://blockexplorer.com/block/00000000000000001e8d6829a8a21adc5d38d0a473b144b6765798e61f98bd1d" rel="nofollow noreferrer">block 125552</a>:</p>

<pre><code>&gt;&gt;&gt; import hashlib
&gt;&gt;&gt; header_hex = ("01000000" +
 "81cd02ab7e569e8bcd9317e2fe99f2de44d49ab2b8851ba4a308000000000000" +
 "e320b6c2fffc8d750423db8b1eb942ae710e951ed797f7affc8892b0f1fc122b" +
 "c7f5d74d" +
 "f2b9441a" +
 "42a14695")
&gt;&gt;&gt; header_bin = header_hex.decode('hex')
&gt;&gt;&gt; hash = hashlib.sha256(hashlib.sha256(header_bin).digest()).digest()
&gt;&gt;&gt; hash.encode('hex_codec')
'1dbd981fe6985776b644b173a4d0385ddc1aa2a829688d1e0000000000000000'
&gt;&gt;&gt; hash[::-1].encode('hex_codec')
'00000000000000001e8d6829a8a21adc5d38d0a473b144b6765798e61f98bd1d'
</code></pre>

<p>Note that the value is reversed at the last step in order to be represented in the big-endian format that we humans are used to.</p>

<blockquote>
  <p>So, this is what I want: the 80 byte input that gives a 32 bit output with a lot of zeros from sha256(sha256(x)).</p>
</blockquote>

<p>You can check these 6 values for every block mined using any one of the many online block explorers available: for example here for the particular block of the previous example: <a href="https://blockexplorer.com/block/00000000000000001e8d6829a8a21adc5d38d0a473b144b6765798e61f98bd1d" rel="nofollow noreferrer">https://blockexplorer.com/block/00000000000000001e8d6829a8a21adc5d38d0a473b144b6765798e61f98bd1d</a> (you'll only have to <a href="https://www.epochconverter.com/" rel="nofollow noreferrer">convert the human time to unix time</a> being careful with the time zone).</p>

<p>Here is a <a href="https://drive.google.com/file/d/1QPDGjz5VXDQsjDZ1TiflEVyY7HOoRIkz/view?usp=sharing" rel="nofollow noreferrer">quick link to download blocks' headers in binary form</a> (until May 2018) and start playing with real values. You <a href="https://bitcoin.stackexchange.com/questions/66873/do-you-know-any-download-site-for-full-blockchain-header-data-6-in-csv-ascii-f/73987#73987">can convert it to .csv</a> if needed.</p>
