I'm coming around to the idea that we _should_ really be using "l" or maybe "r" instead of "zh" for the ழ. At least it's closer in pronunciation and there's a chance someone can work their way to it. Zh is like "we don't have an exact match so we'll repurpose a letter we don't use". It has no phonetic relevance.
Tamil is my mother tongue and I agree 100%. And like insisting that sentences shouldn't end with a preposition, or "you should say GNU/Linux, not Linux", it's no way to make friends and influence people.
Whenever someone says "actually", it's hard not to think of https://www.youtube.com/watch?v=dGvw-E4OtOA