Extract first 1000 lines of zip file

Using unzip I'm attempting to extract the first 1000 lines from an xml file. From reading How to partially extract zipped huge plain text file? I've used the answers to create:

unzip -p my_feed.zip | dd count=1000 > out.txt 

which is close to what I'm trying to achieve.

man dd 

describes :

count=n Copy only n input blocks. 

What is the size of an input block ? How to extract the first 1000 lines instead of first 1000 input blocks ?

Update:

I forgot to mention I'm using osx. I thought this would achieve same result:

gunzip < my_feed.zip | head -n 1000 

but returns error:

gunzip: unknown compression format