That will not work for two reasons:
- Different branded Instant APs will not cluster (Dell, Aruba) as clustering requires the same firmware and you cannot install Aruba firmware on Dell APs.
- Cluster requires the same firmware, and the IAP-135 will go up to Instant 4.2.x, where the IAP-335 will require Instant 4.3.x as the minimum release.
You cannot have two different (version) clusters in the same L2 subnet, unless you have a single AP and can convert that to 'standalone'.