Working with 59.94 frame rate and 23.98 on same sequence

hello, im working on a project thats 1920x1080 23.98, there is a piece that i recorded at 1280x720 @ 59.94 frames that i want to add to the project thats at 23.98 and slow it down smoothly, how can i do this? everything was recorded with a canon mark 3 dslr, when i was recording it i chose 2 different rates on my camera for the 2 different clips i wanted to record my main project is at 23.98 i hope this makes sense, im uaind the 422(HQ) conversion

when i made an extra sequence on final cut and added the 59.94 clip to it and slowed it down on there then added the slowed down sequence to my main project i got an error that i cant have different editing timebases how can i add the 59.94 clip to my 23.98 project and have it slowed down smoothly thanks!

Mac Pro 12Core 2.4
12GB Ram
2TB SSD
Mac OSX 10.6.8

Quadro 4000 & ATI 5770