This relatively new app currently has more than 100 downloads, a 4.4 stars rating from 13 users and the latest APK (version 2.1.1) was from 30th April 2020.
We found these ways of contacting the developers:
Help spread awareness for build verifiability
Please help us spread the word, asking Zumo Bitcoin Wallet: Send & Store Cryptocurrency to support verifiable builds via their Twitter!
The following Analysis is not a full code review! We plan to make code reviews available in the future but even then it will never be a stamp of approval but rather a list of incidents and bad coding practice. We cannot find and tell you all the dark secrets the wallet providers might have.
Do your own research!
Try out searching for "lost bitcoins", "stole my money" or "scammers" together with the wallet's name, even if you think the wallet is generally trustworthy. For all the bigger wallets you will find accusations. Make sure you understand why they were made and if you are comfortable with the provider's reaction.
This app still needs to be evaluated but before that, gain some users. In the Play Store there is an infinite list of "wallets" and we focus on those that have the biggest impact if things go wrong.