At the moment, Zoho Expense does not allow to record a partial reimbursement/payment for the approved expense/claim. However, this feature will available in the future.
To do the partial reimbursement/payment, there are two ways to do it. First by split the expense into two different reports:
1) Split the expenses into two different reports.
2) Approve the expenses.
3) Record the reimbursement on one of the reports for 1st reimbursement payment.
4) Once the payment for 2nd report is made, record the reimbursement payment.
By doing this, the expenses still capture in Zoho Books. However, the payment only captures once the payment has been recorded as reimbursed.