What is the ruling on money whose principal decreases due to zakat, while it is impossible to invest it and usurious interest is avoided, and is it permissible to benefit from the profits of Islamic banks?

Allah promised the pious sustenance from whence they least expect it, as He Almighty says: "And whoever fears Allah - He will make for him a way out And will provide for him from where he does not expect." And zakat (definition) does not truly diminish wealth; rather, it compensates the one who gives zakat with blessings, wards off harms from him, and he earns reward for his obedience, as the Prophet, peace and blessings be upon him, said: "Charity does not decrease wealth."