I didn't know there were conflicts with Mac's and trading platforms. Did you try Etrade Pro? I have used multiple brokers at one time if that is what you are asking. You can do it if you have enough money so that you can have a margin account over 23k in each. If you don't I highly suggest you keep your money in one account so you don't have to worry about pattern day trading rules.
Register for free to join our community of investors and share your ideas. You will also get access to streaming quotes, interactive charts, trades, portfolio, live options flow and more tools.