On the PIC16F877A, all interrupts trigger the same ISR stored at 0x04
.
Therefore, you need something along the lines of:
ORG 0x04
GOTO ISR
Elsewhere:
ISR:
BTFSC INTCON, TMR0IF
GOTO tmr0_ISR
BTFSC PIR1, TMR1IF
GOTO tmr1_ISR
My syntax might not be correct, it's been a while since I've written PIC16 assembly.