Can I trade with zero cash and only collateral margin?

Yes, you can take positions using only collateral margin, but:

For Intraday F&O

No cash requirement. You can use 100% collateral.

For Intraday Positions

No cash requirement. You can use 100% collateral.

For Overnight/Carry-Forward Positions

The 50% cash rule applies. If you use more than 50% non-cash collateral, DPC charges apply on the shortfall amount (0.05% per day).

Note: This means you can still hold overnight positions without cash - you'll just pay interest on the shortfall amount.