In this part of world, working for multiple employer should be seriously considered as it comes with it's own benefits. Here is how to work for multiple employers without having issues.
Delivering value to both employers
Whether working for one, two, three, or more employers, the ability to stay productive is never easy. But there are ways to deliver value to both employers:
Be transparent and set boundaries – To manage expectations, you must let each employer know about your other job(s) and your respective schedules. Be upfront about your availability. Keep at least one hour break between jobs.
Don’t overwork yourself – If you want to manage multiple jobs for a long time, stop killing yourself each day.
Don’t overcommit – It’s easy to feel compelled to take on as much as you can while it’s available. But over-committing yourself can lead to burnout, missed deadlines, or subpar work quality. Know how much you can reasonably handle at one time, and if you have to say ‘no,’ say ‘no.’
Stay focused and avoid distractions. It could be tea/coffee breaks, gossiping with peers, or checking phones. All the short periods you spend on these activities add up to few hours. You could very well use the time to complete your work tasks.
Organize your schedule – You don’t have to keep tasks in your brain. Always make a list of tasks that are assigned to you. Review your to-do list at the start of the day and prioritize tasks. Stick to the order you’ve decided unless your employer asks you something urgently.
Take short breaks – Whether to eat lunch or grab a coffee, take short breaks to unwind and refresh.

If you need more knowledge on how to go about it, without loosing your other job, the benefits of having multiple employers visit the topic "How To Work For Multiple Employers And Deliver Value" from reventify.com