Currently i am using MKR ZERo board, in that ATSAMD21G18A-MUT (48 Pin) is used as microcntroller, but those IO lines are not sufficient for my project.
So i want to use ATSAMD21J18A-MUT (64 pin) in my own hardware.
Is it possible to use the same arduino tool to work with my board which is having ATSAMD21J18A-MUT (64 pin).
If possible what are the changes to be made.
Waiting for a positive reply.
I'd recommend looking at the ATSAMD51P20A. This is the chip used on the Adafruit Grand Central M4:
So Adafruit has already done the work needed for Arduino support in their Adafruit SAMD Boards package, which you can simply install via the Arduino IDE's Boards Manager. That chip ought to give you plenty of IO to play with!
If you're really set on the ATSAMD21J18A, it probably will take a bit of work to add Arduino support, unless you find that someone else happened to already do it for that chip. It shouldn't be too terribly difficult. You can use Arduino SAMD Boards as a starting point, and that will have a lot of the work done for you already. Here's the specification for Arduino hardware packages:
ATSAMD21J18A will work with Arduino SAMD package. you only need to write your boards.txt and pins definition files. here I have an example of custom boards definition