As you have said, Zenyum is a very new clear aligner company. There is very little background information on the official website regarding the technology used for their treatment planning and aligner manufacturing. Zenyum appears to be a collaboration between local orthodontists and tech entrepreneurs.
At the moment, there is no verifiable track record that is available for the public to see. I cannot tell you what software they are using for treatment planning.
I do not know which clinics and orthodontists are officially partnered with Zenyum as this detail is not explicitly stated on the website.
MBrace is another locally-made aligner company with much lower fees compared to Invisalign.
Invisalign has been around the longest and so has the longest track record. Invisalign's strengths are the treatment planning software that has been refined with data from millions of cases over the years and the patented attachment system. These features allow a wider variety of cases to be treated more effectively.
ClearSmile is a UK-based company that caters more to general dentists rather than orthodontic specialists. They offer spring aligners as well as fixed braces systems (including lingual braces) in addition to clear aligners. As far as I know, they do not have a significant footprint in Singapore.
Ultimately, the aligner brand you choose will depend on the practitioner you see as different dentists will have different preferences and varying levels of experience with different aligner systems. For straightforward cases, aligner brand may not be critical since the corrections required may be simple.