No, you cannot use funds available in your equity ledger to trade commodities (or the other way around).

Zerodha facilitates equity and commodity trades through two separate companies - Zerodha Broking Limited and Zerodha Commodities Private Limited. Your equity and commodity funds are maintained separately with these two companies in compliance with regulations. We are working on merging the two companies so that our clients can use one single ledger for their trades.

Presently, if you want to use the funds from the equity segment in commodities (or vice-versa), you will need to first withdraw the funds to your bank account and then add your funds back in the segment of your choosing. See How do I withdraw money from my trading account? and How do I add money to my Zerodha account? to know more.