I've been teaching ZCE for quite a while, originally the 5.0 and 5.3 versions and now the 5.5 certification too, and I hold both certifications myself. One of the hardest things about preparing for the exam is the lack of sample questions available for the 5.5 certification, so I decided to share the set I use with my own ZCE courses. This 60+ page PDF contains some background on the exam and links to resources you will need, plus a set of 70 example ZCE questions (completely unofficial, the aim is to give you an idea of style and content) - complete with correct answers and explanations of those answers.
You can buy the pack from Leanpub: https://leanpub.com/zce
There are a few other things I have published which may help you to prepare (and these don't need your credit card!). When I published this pack, I wrote a blog post giving my best advice for preparing to take the ZCE exam. Also over the last few years I have collected and actively curate a set of links to articles covering some of the topics in the ZCE syllabus, which may be helpful to anyone studying for it. I am also available as a ZCE trainer, offering both public courses and training specifically for your team, just get in touch or take a look at my upcoming courses.