You cannot transfer assets between Fixed and Flexible accounts. You can transfer assets from your Wallet to create Fixed and Flexible accounts.
What to do if I want to transfer assets from a Flexible Account to a Fixed one
You should request a withdrawal from your Flexible Account. When your funds are credited to your Wallet, create a Fixed Account with the desired conditions.
Refer to our article about creating a Fixed Account for more details.
What to do if I want to transfer assets from a Fixed Account to a Flexible one
You should wait till your Fixed Account holding period ends. When the funds are credited to your Wallet, create a Flexible Account with the desired conditions.
Please read our article about creating a Flexible Account for more information.