Want to place trade together in different brokers — will price slip before all orders are placed?

I’m using Zerodha for my own trading, but my clients are on different brokers like Dhan, Angel One, and Fyers.

Now my concern is — if I place a market order, how much delay happens before the same order gets executed across all accounts?

Because in fast markets, even a small delay can change the price.

So will the last broker get a worse price or is this handled properly?