Traditional Islamic understanding
Zakha is traditionally understood as a 2.5% tax on your wealth to be paid annually before Eid-Ul-Fitre. This in no way is a reflection of how much someone is actually worth. A person can earn substantial amounts of money every month, and if he spends it all on a lavish lifestyle, he only needs to pay a measly 2.5% on anything he is left with to help the poor.
It is not possible to fund a system for looking after the vulnerable members of society using this tradition interpretation of Zakha. In this scenario, you would need a separate system to meets the needs of the vulnerable members of society and run community services.
Sam Gerrans interpretation
Zakha has been interpreted by Sam as sexual purity. You can watch his video about it on his YouTube channel. I don’t completely understand why he has translated it as such as a persons sexual purity will have no advantages or disadvantages to the running of a community and helping vulnerable members of society.
The method used by Aasthana is to look at the root word and see how it is being applied with the context of the verses.
The root of the word Zakah is, zāy kāf wāw (ز ك و) = which means ‘to grow,’ ‘to flourish, ‘to bloom,’ ‘to blossom,’ ‘to develop’. it increased/augmented, it grew well/flourished/prospered and produced fruit, put into a good/right state/condition.
So Zakh is referring to growth , progression, development etc something that is not stagnated, something that hasn't failed the ability to develop and attain advanced levels
see the usage in 19:19
"...I shall bestow upon you the gift of a Ghulam endowed with a progressed/ cultivated character." 19:19
The word came repeatedly with Salaat
"aqamoo alssalata and waatawoo alzzakata"
وَأَقَامُوا الصَّلَاةَ وَآتَوُا الزَّكَاةَ
Establish the just socioeconomic system and contribute/
(enable) to its growth/ development
This to me is the most favourable understanding of the word Zakha and meets the needs of the vulnerable members of society as well as running community services for the benefit of all members of the community.
If we take a look at how some countries fund the running of government, it is quite clear that the interpretation of Zakha as illustrated by Aasthana is being implemented. In this scenario, Zakha is now mandatory and implemented by the state and not a voluntary contribution reliant on individuals to make a conscious effort for the sake of earning rewards.