For queries related to Zerodha you can email [email protected], however let me attempt to give you a quick insight here.
Quant is a part of Q.
Q gives you straight forward reports such as - ledger balance value, account value, holding details, open positions, trade reports, P&L, tax P&L etc.
However Quant gives you insights into your own trading pattern. Consider this as an analytical package to gain insights into your trading behavior. If you are familiar with statistics then Quant is very similar to inferential statistics. Some of the interesting reports from Quant - Equity Curve, Time based analytics, Market Trends etc.