FCKEditor was far from perfect. It produced poor markup and required significant hacking of the core Zen Cart code to integrate it, which also means that it doesn't play nicely with other add-ons.
Even the authors recognised that it could be better and have moved on to produce CKEditor as the new generation product.
That said, there's not a lot to choose between CKEditor and TinyMCE. They're both heaps better than HTML editors were barely a year ago.
BUT, neither will allow you to upload images. Both have this facility as a paid-for add-on and require integrations that don't play nicely with Zen Cart.
The background to this is that pushing images from a browser to a server is an inherently insecure approach. It's very easy for hackers to disguise their prodding as a browser and upload dodgy files. Many of the worst hacks have been achieved this way. So image uploaders need to be very secure and actively maintained to ensure that they stay that way.
Moreover, Zen Cart is quite rightly locked down very tightly for security. This is a significant problem in respect of browser based image uploaders, since they're locked out. It is possible to open a hole for them to get through, but the only way I've seen it done securely is to relocate the entire editor and integrate it into the admin. Not for the faint-hearted!
So in summary. You're unlikely to find a good editor, offering the facility that you want, securely. You can pay for it, but even then, may have difficulty integrating it.
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(Questions answered in the forum only - so that any forum member can benefit - not by personal message)