Yes, splitting up the large files is one way to do this. Typically the option you are looking for in WinZip (or whatever ZIP you are using on the PC) is SPANNING. You'd want to enable it, and set the size limit to approx 700kB. (or approx .68MB, if it only allows you to specify in megabytes) I'm not positive which versions of ZIP on the Amiga support SPANNED sets. I think there were some that didn't.....
Other options would include connecting your PC and Amiga with a "null modem" cable. This has the advantage of being able to transfer any file that will fit on the Amiga.... But it has the drawback of being SLooooOOOooWwww, and Error prone, sometimes (unless you use a protocol like Z-Modem that fixes errors) And, of course, you need a terminal on both the Amiga and the PC, and you need to know how to initiate a null modem connection between the two. None of that is horribly difficult, but if you don't remember a good part of back from the old days of 2400 baud modems and local BBSs, it can be a lot to learn all at once.
It's funny that I saw this post right now, because I'm in the same situation, only worse.... I have an A1200, and want to upgrade it to OS3.9. Of course, I don't have a CD ROM on it...... And I want OS3.9 so I get Genesis TCP going, and can use the PCMCIA Network card I found (it's listed as supported by the .device...) ........ But, I have a chicken-and-the-egg style problem. Not easy to transfer a CD image without my networking going.... And not easy to get the networking going without 3.9, which is why I need the CD image..... Hmm.... Bogus. ;-)