[DavidG42]

(A) Finishing the conversation above about Calibre versions:

Having upgraded to the latest 64-bit version, I find that I can convert a 45MB comic from AZW3 to something else (I don't recall whether that worked before), but it still falls over with a memory error at 47% converted for the 75MB comics in the same set. So this didn't solve the problem for the larger files.

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(B) However I have now found a process to extract all the images ready for repackaging into CBZ. (CBZ was my goal in this whole exercise, although it could equally have been CBR or PDF.)

Here's what I did; I hope it helps somebody else who may be facing the same set of problems.

(1) In Calibre, use the Kindle Unpack add-in to convert each of the AZW3 comics files into epub.

Whereas the native Calibre conversion from AZW3 to any other format always got stuck with a memory error at 47% on large AZW3 files (the limit was somewhere between 45MB and 74MB) the Kindle Unpack plug-in worked without a hitch to convert all the files to epub.

(2) In Calibre, select each epub individually, right-click for the context menu, and select "Edit book". Choose the epub format.

(3) In the editor, go to the images folder and highlight all the images.

At this point there is a problem: all the image file-names inside the epub are in random order and do not correspond to the order in which the images appear in the book. Hence the next step.

(4) Right-click (context menu) and select "Bulk rename all selected files". Make sure the "Rename files according to their book order" option is selected. Run the rename process.

(5) Right-click (context menu) and "Export all the selected files".

Now all the image files are extracted into a single folder with file names in logical order.

(6) Finally, it's a trivial process to zip the image files into a single zip file and rename the file as a CBZ file.

.. David

Currently 2 AZW3 files done, another 48 to go ...